(x^3-xy^2)/(7x^2+14xy+7y^2)=(x(x-y)(x+y))/(7(x+y)^2)=(x(x-y))/(7(x+y))=(x^2-xy)/(7x+7y)
x^3-xy^2=x(x^2-y^2)=x(x-y)(x+y)
7x^2+14xy+7y^2=7(x^2+2xy+y^2)=7(x+y)^2
2y^2+6y=0
y(2y+6)=0
1)y=0
2)2y+6=0 2y=-6 y=-3
49-a^2=0
(7-a)(7+a)=0
1)7-a=0 a=7
2)7+a=0 a=0