Find all the zeroes of 2x^4 - 13x^3 19x^2 7x-3 if two of its zeroes ar...
Solution:
Given polynomial is 2x^4 - 13x^3 + 19x^2 + 7x - 3.
Two zeroes of the given polynomial are (2 + √3) and (2 - √3).
Let us find the other zeroes of the polynomial.
By factor theorem, if (2 + √3) is a zero of the given polynomial, then (x - 2 - √3) is a factor of the polynomial.
Similarly, if (2 - √3) is a zero of the given polynomial, then (x - 2 + √3) is a factor of the polynomial.
Now, we can write the polynomial as a product of linear factors as follows:
2x^4 - 13x^3 + 19x^2 + 7x - 3 = 2(x - 2 - √3)(x - 2 + √3)(ax^2 + bx + c)
where a, b, c are constants to be determined.
Expanding the above expression, we get:
2x^4 - 13x^3 + 19x^2 + 7x - 3 = 2(x^2 - 4x + 1)(ax^2 + bx + c)
Multiplying the brackets, we get:
2x^4 - 13x^3 + 19x^2 + 7x - 3 = 2ax^4 + (2bx^3 - 8ax^3) + (2cx^2 - 8bx^2 + x^2) + (-4cx + 7x) - 3c
Equating the coefficients of the like terms on both sides, we get:
2a = 2 => a = 1
2b - 8a = -13 => b = -3
2c - 8b + 1 = 19 => c = 3
-4c + 7 = 7 => c = 0
-3c - 3 = -3 => c = 1
Therefore, the polynomial can be written as:
2x^4 - 13x^3 + 19x^2 + 7x - 3 = 2(x - 2 - √3)(x - 2 + √3)(x^2 - 3x + 1)
The other two zeroes of the polynomial can be found by solving the quadratic factor x^2 - 3x + 1.
Using the quadratic formula, we get:
x = [3 ± √(9 - 4)]/2 = [3 ± √5]/2
Therefore, the four zeroes of the polynomial are:
2 + √3, 2 - √3, [3 + √5]/2, [3 - √5]/2
Hence, the solution.
Find all the zeroes of 2x^4 - 13x^3 19x^2 7x-3 if two of its zeroes ar...