Question

1) (5a+7b)²-70ab
2) (x-8)²-2x(6-x)²
3) -6(2x-y)²  
4) (5+y)²+y(y-7)
5)9b²-(a-3b)²

Answer 1

(5a+7b)²-70ab = 25a²+70ab+49b²-70ab = 25a²+49b²

(x-8)²-2x(6-x)² = x²-16x+64-2x(36-12x+x²) = x²-16x+64-72x+24x²-2x3=2x3+25x²-8x+64

-6(2x-y)²= -6(4x²-4xy+y²)= -24x²+24xy-6y²

(5+y)²+y(y-7) =25+10y+y²+y²-7y=2y²+3y+25

 9b²-(a-3b)²=9b²-a²-6ba+9b² =18b²-a²-6ba