Answer:
a)
(3-x)^2 = (3-x)(3-x) = 9 - 6x + x^2
(3x + 4y)^2 = (3x + 4y)(3x + 4y) = 9x^2 + 24xy + 16y^2
So, (3-x)^2 * (3x+4y)^2 = (9 - 6x + x^2) * (9x^2 + 24xy + 16y^2) = 144x^2 - 108x^3 - 192xy + 144y^2 + 9x^4 - 32y^2x^2 + 16y^4
b)
(7x - 5) (7x + 5)^2 = (7x - 5) (49x^2 + 70x + 25) = 343x^3 - 50x^2 - 175x - 125
c)
8x(x-4) - (x-6)(x+6) = 8x^2 - 32x - (x^2 - 36) = 7x^2 - 32x + 36