Question

Which of the binomials below is a factor of this trinomial x^2+14x+40

A: X+14
B: x-9
C: x^2+4
D: x+10

Answer 1

`x^2+14x+40=\\ x^2+4x+10x+40=\\ x(x+4)+10(x+4)=0\\ (x+10)(x+4)`

So it's D.