Răspuns :
a) (2x-3y)(5x+7y-1)=(2x*5x)+(2x*7y)-(2x*1)-(3y*5x)-(3y*7y)+(3y*1)=10x²+14xy-2x-15xy-21y²+3y=10x²-xy-2x-21y²+3y=10x²-21y²-xy-2x+3y
b)(a-b)(a²+ab+b²)=(a*a²)+(a*ab)+(a*b²)-(b*a²)-(b*ab)-(b*b²)=a³+a²b+ab²-a²b-ab²-b³=a³-b³
b)(a-b)(a²+ab+b²)=(a*a²)+(a*ab)+(a*b²)-(b*a²)-(b*ab)-(b*b²)=a³+a²b+ab²-a²b-ab²-b³=a³-b³
a)(2x-3y)(5x+7y-1)=10x²+14xy-2x-15xy-21y²+3y=10x²-21y²-xy+3y=x(10x-y)+3y(1-7y)
b)(a-b)(a²+ab+b²)=a³+a²b+ab²-a²b-ab²-b³=a³-b³
b)(a-b)(a²+ab+b²)=a³+a²b+ab²-a²b-ab²-b³=a³-b³
