[tex]\displaystyle \it a).(x+3)^2+(5-x)^2=x^2+2 \cdot x \cdot 3+3^2+5^2-2 \cdot 5 \cdot x+x^2= \\ =x^2+6x+9+25-10x+x^2=2x^2-4x+34 \\ b).(y+2)^2+(7-y)^2=y^2+2 \cdot y \cdot 2+2^2+7^2-2 \cdot 7 \cdot y+y^2= \\ =y^2+4y+4+49-14y+y^2=2y^2-10y+53 \\ \\ \boxed{(a+b)^2=a^2+2ab+b^2} ~~~~~~~~~~~~~~~~~~~~~~\boxed{(a-b)^2=a^2-2ab+b^2}[/tex]
