Question

if (2x+3) (5x-7)=10xsquare -kx-21,then the value of k is​

Answer 1

(2x+3)(5x-7)=10x²-kx-21

2x(5x-7)+3(5x-7)=10x²-kx-21

10x²-14x+15x-21=10x²-kx-21

10x²+x-21=10x²-kx-21

10x²and 21 will get cancelled.

Hence,x=-kx

-k=x/x

-k=1

k=-1

Therefore, the value of k is -1.