Question

若x-2y=2 x+2y=6 则x的平方-4y的平方+2x-4y=?

Answer 1

x²-4y²+2x-4y

=(x²-4y²)+(2x-4y)

=(x+2y)(x-2y)+2(x-2y)

=(x-2y)(x+2y+2)

=2×(6+2)

=2×8

=16