Question

(x+10)(x+3)=x2+(10+3)x+10.3

Answer 1

(x+10)(x+3)=x²+(10+3)x+(10·3)
x²+3x+10x+30=x²+10x+3x+30
x²-x²+13x-3x=30-30
10x=0
x=0/10
x=0

Saludos!