Math help please
posted by Marina .
1.) 4(2a)^281
2.) (xy)^3
3.)3x^227(2x)^2
4.) 9(y1)^225

1. 4(2a)^2  81 , difference of squares
= (2(2a) + 9)(2(2a)  9)
=(4  2a +9)(4 2a  9)
= (2a + 13)(2a  5)
or
(2a13)(2a+5) , I wanted to start the brackets with a positive so I multiplies by (1)(1)
Do #4 the same way.
3.
3x^2  27(2x)^2
= 3[x^2  9(2x)} , again a difference of square
= 3(x  3(2x))(x + 3(2x))
= 3(x  6 + 3x)(x + 6  3x)
= 3(4x6)(62x)
= 3(2)(2)(2x3)(3x)
= 12(2x3)(3x)
For #2,
(x)(xy)(xy)
= (xy)(x^2  2xy + y^2)
=  (x^3  2x^2y + xy^2  yx^2 + 2xy^2  y^3)
=  x^3 + 3yx^2 3xy^2 + y^3