1) 9а^2 - p^2 + p^2 = 9а^2 - (p^2 + p^2) = 9a^2 - 0 = 9a^2
2) (a + 11)(a + 11) - 20a = a^2 + 22a + 121 - 20a =a^2 +(22a - 20a) + 121 = a^2 + 2a +121
3) 25a^2 - (c^2 - 25a^2) = 25a^2 - c^2 + 25a^2 = 50a^2 - c^2
4) 4x^2 - (x - 3y)(x - 3y) = 4x^2 - (x^2 - 6y + 9y^2) = 4x^2 - x^2 +6y - 9y^2 = 3x^2 + 6y - 9y^2
5) a^2 - 4b^2 - a + b
6) (y + x)(y + x) - (y - x)(y - x) = (y^2 + 2yx + x^2) - ( y^2 - 2yx + x^2) = y^2 + 2yx + x^2 - y^2 + 2yx - x^2 = 0 +4yx + 0 =4yx
7) (a - 2b)(a - 2b) + (a^2 - 4b^2) = a^2 - 4ab + 4b^2 + a^2 - 4b^2 = 2a^2 - 4ab + 0 = 2a^2 - 4ab
8) (a - 5x)(a - 5x) + (a + 5x)(a + 5x) = a^2 - 10ax + 25x^2 + a^2 + 10ax + 25x^2 = 2a^2 - 0 + 50x^2 = 2a^2 +50x^2
9) b^2 - 1 - a^2 + 1 = b^2 - 0 - a^2 = b^2 - a^2
10) 9a^2 - 4 + a^2 - 16 = 10a^2 + 20