Question

X-3 and 2x-1 are factors of 2x^3-px^2-2qx+q. Find the values of p and q.

Answer 1

Answer:

p =1

q = 9

Step-by-step explanation:

f(x) = 2x³ - px² + 2qx + q

(x - 3) is a factor of f(x)

⇒f(3)  = 0

2(3)³ - p*3² - 2q*3 +q = 0

2*27 - 9p - 6q + q = 0

    54 - 9p - 5q = 0

            -9p - 5q = -54 -------------------(I)

(2x - 1) is a factor of f(x)

2x - 1 = 0

      2x = 1

        $\st x = \dfrac{1}{2}$

f(1/2) = 0

$2*(\dfrac{1}{2})^{3}-p*(\dfrac{1}{2})^{2}-2q*\dfrac{1}{2}+q=0\\\\2*\dfrac{1}{8}-p*\dfrac{1}{4}-q+q = 0\\\\\dfrac{1}{4}-\dfrac{1}{4}p =0\\\\[Multiply the entire equation by 4]\\\\4*\dfrac{1}{4}-4*\dfrac{1}{4}p=0$

1 - p = 0

    -p = -1

p = 1

Substitute p =1 in equation (I)

-9*1 - 5q = -54

 -9 - 5q = -54

      -5q = -54 + 9

      -5q = -45

           q = -45/(-5)

q = 9