Question

1.（x-3y)(x+3y)-(x-3y)^2 2.98^2 3.(2x-y-3)(2x+y+3) 4.50.1^2 5

Answer 1

1.（x-3y)(x+3y)-(x-3y)^2

=(x-3y)[(x+3y)-(x-3y)]

=6y(x-3y)

2.98^2

=(100-2)^2

=100^2-2x100x2+2^2

=10000-400+4

=99604

3.(2x-y-3)(2x+y+3)

=(2x)^2-(y+3)^2

=4x^2-y^2-6y-9

4.50.1^2

=(50+0.1)^2

=50^2+2x50x0.1+0.1^2

=2500+10+0.01

=2510.01

5.(5x+7y)^2-(5x-7y)^2

=[(5x+7y)+(5x-7y)][(5x+7y)-(5x-7y)]

=140xy