Question

The value of polynomial 5x cube + kx square +2x-14 at x=2 is more than its value at x=-1.Find k

Answer 1

P(x)= 5x^3+kx^2+2x-14

For x=2,

P(2)= 5(8) + k(4) + 2(2) - 14

P(2)= 40 + 4k + 4 - 14

P(2)= 40 - 10 + 4k

P(2)= 30 + 4k ....(1)

Since,

x=2 satisfies the equation

Therefore,

P(2)= 0 ....(2)

From (1) & (2),we get,

30+4k=0

4k= -30

k= -30/4

k= -15/2