Question

If one zero of the polynomial x2-5x+k is -4,then find the value of k.Find the other zero also.

Answer 1

Given

x²-5x+k=0

one root of the equation=-4

To find

the value of k and another root

substituting x=-4 in given equation because given -4 is one of the root

(-4)²-5(-4)+k=0

16+20+k=0

k+36=0

k=-36

then the equation is x²-5x-36=0

x²+4x-9x-36=0

x(x+4)-9(x+4)=0

(x+4)(x-9)=0

x=-4,9

the another root of the equation is 9

thank you

Answer 2

Answer:

Given:

x²-5x+k=0

one root of the equation= -4

To Prove:

find the value of k

Proof:

x²-5x+k =0

16+20+k=0

k+36=0

k= -36

then the equation is x²-5x -36=0

x²+4x-9x-36=0

x(x+4)-9(x+4)=0

(x+4)(x-9)=0

x= -4, 9