Question

Solve by factorising.
x2 + 10x + 21 = 0

Answer 1

×=-7,×=-3

Explanation:

plz don't mind my "×"

×^2+10×+21=0

×^2+7×+3×+21=0

rearrange

that is ; ×^2+3×+7×+21=0

(×^2+3×)+(7×+21)=0

×(×+3)+7 (×+3)=0

therefore

(×+7) (×+3)=0

×+7=0 ×+3=0

×= -7 ×=-3