## kryton1212 Let P(x)=kx^(3)-9x^(2)-15x+50. (a) If 2x+5 is a factor of P(x), find the value of k. (b) Factorize P(x) completely. one year ago one year ago

1. .Sam.

If 2x+5 is a factor of P(x) Then P(-5/2) = k(-5/2)^(3)-9(-5/2)^(2)-15(-5/2)+50 =0 Find k..

2. .Sam.

You can equate to zero because its a factor of P(x), then -5/2 as value for x

3. kryton1212

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4. .Sam.

P(-5/2) = k(-5/2)^3+125/4 =0 P(-5/2) = k(-5/2)^3 = -125/4

5. kryton1212

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6. .Sam.

There's something wrong with your calculations, k should be 2

7. kryton1212

i know, but i don't know where i wrong

8. kryton1212

i know, it should be 75..

9. .Sam.

$-\frac{125}{8}k-\frac{225}{4}+\frac{75}{2}+50=0$ Multiply by 8, $-125k-450+300+400=0 \\ \\ -125k+250=0 \\ \\ k=2$

10. kryton1212

i got it

11. kryton1212

thanks