Question

if x=4 then 5x³-7x²-kx-28 then find the value of k​

Answer 1

Answer:

Let, f (x) = 5x³ - 7x² - kx - 28 be the given polynomial.

By factor theorem,  If (x - 4) is a factor of f (x) then f (4) = 0  :

Now, f (x) = 5x³ - 7x² - kx - 28  

⇒f (4) = 5(4)³ - 7(4)² + k (4) - 28

⇒ 0 = 5 × 64 - 7 × 16 + 4k - 28

⇒ 0 = 320 - 112 + 4k - 28

⇒0 = 180 -  4k

⇒5k = 180

⇒k = 180/5

⇒k = 45

Hence, (x – 4) is a factor of f (x), if k is 45.

HOPE THIS ANSWER WILL HELP YOU…..

_____________________________________

Answer 2

Answer:

GIVEN:-

IF X= 4

So,

So,5x³-7x²-kx-28

So,5x³-7x²-kx-28 The value of K is

Step-by-step explanation:

Solution:-

5(4)³-7(4)²-k(4)-28=0

5(64)-7(16)-4k-28=0

320-112-4k-28=0

180-4k=0

-4k=-180

K=-180/-4

K=45

Ans —The value of k is 45.