RD Sharma Solutions - Ex - 7.3, Algebraic Expressions, Class 7, Math Class 7 Notes | EduRev

RD Sharma Solutions for Class 7 Mathematics

Created by: Abhishek Kapoor

Class 7 : RD Sharma Solutions - Ex - 7.3, Algebraic Expressions, Class 7, Math Class 7 Notes | EduRev

The document RD Sharma Solutions - Ex - 7.3, Algebraic Expressions, Class 7, Math Class 7 Notes | EduRev is a part of the Class 7 Course RD Sharma Solutions for Class 7 Mathematics.
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Question 1:

Place the last two terms of the following expressions in parentheses preceded by a minus sign:
 (i) xy − 3zy
 (ii) 3x − 2y − 5z − 4
 (iii) 3a − 2b + 4c − 5
 (iv) 7a + 3b + 2c + 4
 (v) 2a2 − b2 − 3ab + 6
 (vi) a2 + b2 − c2ab − 3ac

Answer 1:

We have
(i) x + y − 3z + y = x  + y − (3z - y )
(ii) 3x − 2y − 5z − 4 = 3x - 2y - (5z + 4)
(iii) 3a − 2b + 4c − 5 = 3a - 2b - (- 4c + 5)
(iv) 7a + 3b + 2c + 4 = 7a + 3b - (- 2c - 4)
(v) 2a2 − b2 − 3ab + 6 = 2a2 − b2 − (3ab - 6)
(vi) a2 + b2 − c2 + ab − 3ac = a2 + b2 − c2 - (- ab + 3ac)

Question 2:

Write each of the following statements by using appropriate grouping symbols:
 (i) The sum of a − b and 3a − 2b + 5 is subtracted from 4a + 2b − 7.
 (ii) Three times the sum of 2xy − {5 − (x − 3y)} and 7x − 4y + 3 is subtracted from 3x − 4y + 7.
 (iii) The subtraction of x2 − y2 + 4xy from 2x2y2 − 3xy is added to 9x2 − 3y2 − xy.

Answer 2:

(i) The sum of a − b and 3a − 2b + 5 = {(a - b) + (3a − 2b + 5)}.
     This is subtracted from 4a + 2b - 7.
     Thus, the required expression is {4a + 2b - 7) - {(a - b) + (3a − 2b + 5)}.

(ii) Three times the sum of 2x + y − {5 − (x − 3y)} and 7x − 4y + 3 = 3[(2x + y) − {5 − (x − 3y)} + (7x − 4y + 3)].
      This is subtracted from 3x - 4y +7.
      Thus, the required expression is (3x - 4y +7) - 3[(2x + y) − {5 − (x − 3y)} + (7x − 4y + 3)].

(iii) The product of subtraction of x2 − y2 + 4xy from 2x2 + y2 − 3xy is given by {(2x2 + y2 − 3xy) - (x2 − y2 + 4xy)}.
       When the above equation is added to 9x2 − 3y2 − xy, we get
       {(2x2 + y2 − 3xy) - (x2 − y2 + 4xy)} + (9x2 − 3y2 − xy)

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