$$^{(x+y)^2=x^2+y^2+xy}$$
$$(X-y^2)=x^2+y^2-xy$$
$$X^2-y^2=(x+y)(x-y)$$
$$X(x+y+z)^2=x^2+y^2+z^2+2(xy+yz+xz)$$
- (X+a) (x+b) = x² +(a+b)x + ab
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$$^{(x+y)^2=x^2+y^2+xy}$$
$$(X-y^2)=x^2+y^2-xy$$
$$X^2-y^2=(x+y)(x-y)$$
$$X(x+y+z)^2=x^2+y^2+z^2+2(xy+yz+xz)$$