Question

Answer 1

\(a,5x-xy+y^2-5y=x\left(5-y\right)-y\left(5-y\right)=\left(x-y\right)\left(5-y\right)\\ b,x^2+2x+1-y^2=\left(x+1\right)^2-y^2=\left(x-y+1\right)\left(x+y+1\right)=\left(84-15+1\right)\left(84+15+1\right)=70.100=7000\)

Answer 2

a: \(=5\left(x-y\right)-y\left(x-y\right)=\left(x-y\right)\left(5-y\right)\)