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Page 2 We have: 4x 2 -9y 2 = (2x) 2 -(3y) 2 = (2x +3y)(2x -3y) ? 4x 2 -9y 2 = (2x +3y)(2x -3y) Q u e s t i o n : 3 3 Factorise: 16a 2 - 225b 2 S o l u t i o n : We have: 16a 2 -225b 2 = (4a) 2 -(15b) 2 = (4a +15b)(4a -15b) ? 16a 2 -225b 2 = (4a +15b)(4a -15b) Q u e s t i o n : 3 4 Factorise: 9a 2 b 2 - 25 S o l u t i o n : We have: 9a 2 b 2 -25 = (3ab) 2 -(5) 2 = (3ab +5)(3ab -5) ? 9a 2 b 2 -25 = (3ab +5)(3ab -5) Q u e s t i o n : 3 5 Factorise: 16a 2 - 144 S o l u t i o n : We have: 16a 2 -144 = (4a) 2 -(12) 2 = (4a +12)(4a -12) = 4 a + 3 4 a -3 = 16 a +3 a -3 ? 16a 2 -144 = 16(a +3)(a -3) Q u e s t i o n : 3 6 Factorise: 63a 2 - 112b 2 S o l u t i o n : We have: 63a 2 -112b 2 = 7 9a 2 -16b 2 = 7 (3a) 2 -(4b) 2 = 7(3a +4b)(3a -4b) ? 63a 2 -112b 2 = 7(3a +4b)(3a -4b) Q u e s t i o n : 3 7 Factorise: 20a 2 - 45b 2 S o l u t i o n : We have: 20a 2 -45b 2 = 5 4a 2 -9b 2 = 5 (2a) 2 -(3b) 2 = 5(2a +3b)(2a -3b) ? 20a 2 -45b 2 = 5(2a +3b)(2a -3b) Q u e s t i o n : 3 8 Factorise: 12x 2 - 27 S o l u t i o n : We have: 12x 2 -27 = 3 4x 2 -9 = 3 (2x) 2 -(3) 2 = 3(2x +3)(2x -3) ? 12x 2 -27 = 3(2x +3)(2x -3) Q u e s t i o n : 3 9 Factorise: x 3 - 64x S o l u t i o n : We have: x 3 -64x = x x 2 -64 = x (x) 2 -(8) 2 = x(x +8)(x -8) ? x 3 -64x = x(x +8)(x -8) Q u e s t i o n : 4 0 Factorise: 16x 5 - 144x 3 S o l u t i o n : We have: 16x 5 -144x 3 = 16x 3 x 2 -9 = 16x 3 (x) 2 -(3) 2 = 16x 3 (x +3)(x -3) ? 16x 5 -144x 3 = 16x 3 (x +3)(x -3) Q u e s t i o n : 4 1 ( ) ( ) ( ) ( ) ( ) { } ( ) { } ( ) { } ( ) { } ( ) { } Page 3 We have: 4x 2 -9y 2 = (2x) 2 -(3y) 2 = (2x +3y)(2x -3y) ? 4x 2 -9y 2 = (2x +3y)(2x -3y) Q u e s t i o n : 3 3 Factorise: 16a 2 - 225b 2 S o l u t i o n : We have: 16a 2 -225b 2 = (4a) 2 -(15b) 2 = (4a +15b)(4a -15b) ? 16a 2 -225b 2 = (4a +15b)(4a -15b) Q u e s t i o n : 3 4 Factorise: 9a 2 b 2 - 25 S o l u t i o n : We have: 9a 2 b 2 -25 = (3ab) 2 -(5) 2 = (3ab +5)(3ab -5) ? 9a 2 b 2 -25 = (3ab +5)(3ab -5) Q u e s t i o n : 3 5 Factorise: 16a 2 - 144 S o l u t i o n : We have: 16a 2 -144 = (4a) 2 -(12) 2 = (4a +12)(4a -12) = 4 a + 3 4 a -3 = 16 a +3 a -3 ? 16a 2 -144 = 16(a +3)(a -3) Q u e s t i o n : 3 6 Factorise: 63a 2 - 112b 2 S o l u t i o n : We have: 63a 2 -112b 2 = 7 9a 2 -16b 2 = 7 (3a) 2 -(4b) 2 = 7(3a +4b)(3a -4b) ? 63a 2 -112b 2 = 7(3a +4b)(3a -4b) Q u e s t i o n : 3 7 Factorise: 20a 2 - 45b 2 S o l u t i o n : We have: 20a 2 -45b 2 = 5 4a 2 -9b 2 = 5 (2a) 2 -(3b) 2 = 5(2a +3b)(2a -3b) ? 20a 2 -45b 2 = 5(2a +3b)(2a -3b) Q u e s t i o n : 3 8 Factorise: 12x 2 - 27 S o l u t i o n : We have: 12x 2 -27 = 3 4x 2 -9 = 3 (2x) 2 -(3) 2 = 3(2x +3)(2x -3) ? 12x 2 -27 = 3(2x +3)(2x -3) Q u e s t i o n : 3 9 Factorise: x 3 - 64x S o l u t i o n : We have: x 3 -64x = x x 2 -64 = x (x) 2 -(8) 2 = x(x +8)(x -8) ? x 3 -64x = x(x +8)(x -8) Q u e s t i o n : 4 0 Factorise: 16x 5 - 144x 3 S o l u t i o n : We have: 16x 5 -144x 3 = 16x 3 x 2 -9 = 16x 3 (x) 2 -(3) 2 = 16x 3 (x +3)(x -3) ? 16x 5 -144x 3 = 16x 3 (x +3)(x -3) Q u e s t i o n : 4 1 ( ) ( ) ( ) ( ) ( ) { } ( ) { } ( ) { } ( ) { } ( ) { } Factorise: 3x 5 - 48x 3 S o l u t i o n : We have: 3x 5 -48x 3 = 3x 3 x 2 -16 = 3x 3 (x) 2 -(4) 2 = 3x 3 (x +4)(x -4) ? 3x 5 -48x 3 = 3x 3 (x +4)(x -4) Q u e s t i o n : 4 2 Factorise: 16p 3 - 4p S o l u t i o n : We have: 16p 3 -4p = 4p 4p 2 -1 = 4p (2p) 2 -(1) 2 = 4p(2p +1)(2p -1) ? 16p 3 -4p = 4p(2p +1)(2p -1) Q u e s t i o n : 4 3 Factorise: 63a 2 b 2 - 7 S o l u t i o n : We have: 63a 2 b 2 -7 = 7 9a 2 b 2 -1 = 7 (3ab) 2 -(1) 2 = 7(3ab +1)(3ab -1) ? 63a 2 b 2 -7 = 7(3ab +1)(3ab -1) Q u e s t i o n : 4 4 Factorise: 1 - b -c 2 S o l u t i o n : We have: 1 -(b -c) 2 = (1) 2 -(b -c) 2 = {1 +(b -c)}{1 -(b -c)} = (1 +b -c)(1 -b +c) ? 1 -(b -c) 2 = (1 +b -c)(1 -b +c) Q u e s t i o n : 4 5 Factorise: (2a + 3b) 2 - 16c 2 S o l u t i o n : We have: (2a +3b) 2 -16c 2 = (2a +3b) 2 -(4c) 2 = {(2a +3b)+4c}{(2a +3b)-4c} = (2a +3b +4c)(2a +3b -4c) ? (2a +3b) 2 -16c 2 = (2a +3b +4c)(2a +3b -4c) Q u e s t i o n : 4 6 Factorise: (l + m) 2 - (l - m) 2 S o l u t i o n : We have: (l +m) 2 -(l -m) 2 = {(l +m)+(l -m)}{(l +m)-(l -m)} = (l +m +l -m)(l +m -l +m) = (2l)(2m) ? (l +m) 2 -(l -m) 2 = (2l)(2m) Q u e s t i o n : 4 7 Factorise: (2x + 5y) 2 - 1 S o l u t i o n : We have: (2x +5y) 2 -1 = (2x +5y) 2 -(1) 2 = {(2x +5y)+1}{(2x +5y)-1} = (2x +5y +1)(2x +5y -1) ? (2x +5y) 2 -1 = (2x +5y +1)(2x +5y -1) Q u e s t i o n : 4 8 Factorise: 36c 2 - (5a + b) 2 S o l u t i o n : We have: 36c 2 -(5a +b) 2 = (6c) 2 -(5a +b) 2 = {(6c)+(5a +b)}{(6c)-(5a +b)} = (6c +5a +b)(6c -5a -b) ? 36c 2 -(5a +b) 2 = (6c +5a +b)(6c -5a -b) Q u e s t i o n : 4 9 Factorise: (3x - 4y) 2 - 25z 2 S o l u t i o n : We have: (3x -4y) 2 -25z 2 = (3x -4y) 2 -(5z) 2 = {(3x -4y)+5z}{(3x -4y)-5z} = (3x -4y +5z)(3x -4y -5z) ? (3x -4y) 2 -25z 2 = (3x -4y +5z)(3x -4y -5z) ( ) { } ( ) { } ( ) { } Page 4 We have: 4x 2 -9y 2 = (2x) 2 -(3y) 2 = (2x +3y)(2x -3y) ? 4x 2 -9y 2 = (2x +3y)(2x -3y) Q u e s t i o n : 3 3 Factorise: 16a 2 - 225b 2 S o l u t i o n : We have: 16a 2 -225b 2 = (4a) 2 -(15b) 2 = (4a +15b)(4a -15b) ? 16a 2 -225b 2 = (4a +15b)(4a -15b) Q u e s t i o n : 3 4 Factorise: 9a 2 b 2 - 25 S o l u t i o n : We have: 9a 2 b 2 -25 = (3ab) 2 -(5) 2 = (3ab +5)(3ab -5) ? 9a 2 b 2 -25 = (3ab +5)(3ab -5) Q u e s t i o n : 3 5 Factorise: 16a 2 - 144 S o l u t i o n : We have: 16a 2 -144 = (4a) 2 -(12) 2 = (4a +12)(4a -12) = 4 a + 3 4 a -3 = 16 a +3 a -3 ? 16a 2 -144 = 16(a +3)(a -3) Q u e s t i o n : 3 6 Factorise: 63a 2 - 112b 2 S o l u t i o n : We have: 63a 2 -112b 2 = 7 9a 2 -16b 2 = 7 (3a) 2 -(4b) 2 = 7(3a +4b)(3a -4b) ? 63a 2 -112b 2 = 7(3a +4b)(3a -4b) Q u e s t i o n : 3 7 Factorise: 20a 2 - 45b 2 S o l u t i o n : We have: 20a 2 -45b 2 = 5 4a 2 -9b 2 = 5 (2a) 2 -(3b) 2 = 5(2a +3b)(2a -3b) ? 20a 2 -45b 2 = 5(2a +3b)(2a -3b) Q u e s t i o n : 3 8 Factorise: 12x 2 - 27 S o l u t i o n : We have: 12x 2 -27 = 3 4x 2 -9 = 3 (2x) 2 -(3) 2 = 3(2x +3)(2x -3) ? 12x 2 -27 = 3(2x +3)(2x -3) Q u e s t i o n : 3 9 Factorise: x 3 - 64x S o l u t i o n : We have: x 3 -64x = x x 2 -64 = x (x) 2 -(8) 2 = x(x +8)(x -8) ? x 3 -64x = x(x +8)(x -8) Q u e s t i o n : 4 0 Factorise: 16x 5 - 144x 3 S o l u t i o n : We have: 16x 5 -144x 3 = 16x 3 x 2 -9 = 16x 3 (x) 2 -(3) 2 = 16x 3 (x +3)(x -3) ? 16x 5 -144x 3 = 16x 3 (x +3)(x -3) Q u e s t i o n : 4 1 ( ) ( ) ( ) ( ) ( ) { } ( ) { } ( ) { } ( ) { } ( ) { } Factorise: 3x 5 - 48x 3 S o l u t i o n : We have: 3x 5 -48x 3 = 3x 3 x 2 -16 = 3x 3 (x) 2 -(4) 2 = 3x 3 (x +4)(x -4) ? 3x 5 -48x 3 = 3x 3 (x +4)(x -4) Q u e s t i o n : 4 2 Factorise: 16p 3 - 4p S o l u t i o n : We have: 16p 3 -4p = 4p 4p 2 -1 = 4p (2p) 2 -(1) 2 = 4p(2p +1)(2p -1) ? 16p 3 -4p = 4p(2p +1)(2p -1) Q u e s t i o n : 4 3 Factorise: 63a 2 b 2 - 7 S o l u t i o n : We have: 63a 2 b 2 -7 = 7 9a 2 b 2 -1 = 7 (3ab) 2 -(1) 2 = 7(3ab +1)(3ab -1) ? 63a 2 b 2 -7 = 7(3ab +1)(3ab -1) Q u e s t i o n : 4 4 Factorise: 1 - b -c 2 S o l u t i o n : We have: 1 -(b -c) 2 = (1) 2 -(b -c) 2 = {1 +(b -c)}{1 -(b -c)} = (1 +b -c)(1 -b +c) ? 1 -(b -c) 2 = (1 +b -c)(1 -b +c) Q u e s t i o n : 4 5 Factorise: (2a + 3b) 2 - 16c 2 S o l u t i o n : We have: (2a +3b) 2 -16c 2 = (2a +3b) 2 -(4c) 2 = {(2a +3b)+4c}{(2a +3b)-4c} = (2a +3b +4c)(2a +3b -4c) ? (2a +3b) 2 -16c 2 = (2a +3b +4c)(2a +3b -4c) Q u e s t i o n : 4 6 Factorise: (l + m) 2 - (l - m) 2 S o l u t i o n : We have: (l +m) 2 -(l -m) 2 = {(l +m)+(l -m)}{(l +m)-(l -m)} = (l +m +l -m)(l +m -l +m) = (2l)(2m) ? (l +m) 2 -(l -m) 2 = (2l)(2m) Q u e s t i o n : 4 7 Factorise: (2x + 5y) 2 - 1 S o l u t i o n : We have: (2x +5y) 2 -1 = (2x +5y) 2 -(1) 2 = {(2x +5y)+1}{(2x +5y)-1} = (2x +5y +1)(2x +5y -1) ? (2x +5y) 2 -1 = (2x +5y +1)(2x +5y -1) Q u e s t i o n : 4 8 Factorise: 36c 2 - (5a + b) 2 S o l u t i o n : We have: 36c 2 -(5a +b) 2 = (6c) 2 -(5a +b) 2 = {(6c)+(5a +b)}{(6c)-(5a +b)} = (6c +5a +b)(6c -5a -b) ? 36c 2 -(5a +b) 2 = (6c +5a +b)(6c -5a -b) Q u e s t i o n : 4 9 Factorise: (3x - 4y) 2 - 25z 2 S o l u t i o n : We have: (3x -4y) 2 -25z 2 = (3x -4y) 2 -(5z) 2 = {(3x -4y)+5z}{(3x -4y)-5z} = (3x -4y +5z)(3x -4y -5z) ? (3x -4y) 2 -25z 2 = (3x -4y +5z)(3x -4y -5z) ( ) { } ( ) { } ( ) { } Q u e s t i o n : 5 0 Factorise: x 2 - y 2 - 2y - 1 S o l u t i o n : We have: x 2 -y 2 -2y -1 = x 2 - y 2 +2y +1 = (x) 2 -(y +1) 2 = {x +(y +1)}{x -(y +1)} = (x +y +1)(x -y -1) ? x 2 -y 2 -2y -1 = (x +y +1)(x -y -1) Q u e s t i o n : 5 1 Factorise: 25 - a 2 - b 2 - 2ab S o l u t i o n : We have: 25 -a 2 -b 2 -2ab = 25 - a 2 +b 2 +2ab = 25 -(a +b) 2 = (5) 2 -(a +b) 2 = {5 +(a +b)}{5 -(a +b)} = (5 +a +b)(5 -a -b) ? 25 -a 2 -b 2 -2ab = (5 +a +b)(5 -a -b) Q u e s t i o n : 5 2 Factorise: 25a 2 - 4b 2 + 28bc - 49c 2 S o l u t i o n : We have: 25a 2 -4b 2 +28bc -49c 2 = 25a 2 - 4b 2 -28bc +49c 2 = (5a) 2 -(2b -7c) 2 = {5a +(2b -7c)}{5a -(2b -7c)} = (5a +2b -7c)(5a -2b +7c) ? 25a 2 -4b 2 +28bc -49c 2 = (5a +2b -7c)(5a -2b +7c) Q u e s t i o n : 5 3 Factorise: 9a 2 - b 2 + 4b - 4 S o l u t i o n : We have: 9a 2 -b 2 +4b -4 = 9a 2 - b 2 -4b +4 = (3a) 2 -(b -2) 2 = {3a +(b -2)}{3a -(b -2)} = (3a +b -2)(3a -b +2) ? 9a 2 -b 2 +4b -4 = (3a +b -2)(3a -b +2) Q u e s t i o n : 5 4 Factorise: 100 - (x - 5) 2 S o l u t i o n : We have: 100 -(x -5) 2 = (10) 2 -(x -5) 2 = {10 +(x -5)}{10 -(x -5)} = (10 +x -5)(10 -x +5) = (5 +x)(15 -x) ? 100 -(x -5) 2 = (5 +x)(15 -x) Q u e s t i o n : 5 5 Factorise: Evaluate {405 2 - 395 2 }. S o l u t i o n : We have: (405) 2 -(395) 2 = (405 +395)(405 -395) = (800 ×10) = 8000 ? (405) 2 -(395) 2 = 8000 Q u e s t i o n : 5 6 Factorise: Evaluate {7.8 2 - 2.2 2 }. S o l u t i o n : We have: (7. 8) 2 -(2. 2) 2 = (7. 8 +2. 2)(7. 8 -2. 2) = (10 ×5. 6) = 56 ? (7. 8) 2 -(2. 2) 2 = 56 ( ) ( ) ( ) ( ) { } { } { } { }Read More
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