1a. 3x2 - 2x(5 + 1,5x) + 10 = 3x2 - 10x + 3x2 = 6x2 - 10x
b. (2x - 3)(x + 7) - 2x(x+5) - x = 2x2 - 3x - 3x - 21 - 2x2 - 10x = -16x - 21
c. (x + 3)(x - 3) - (x - 5)(x + 2) = x2 - 32 - (x2 + 2x - 5x - 10) = x2 - 9 - x2 - 2x + 5x + 10 = 3x + 1
d. (x - 1)2 - (x + 2)(x - 2) = x2 - 2x + 1 - (x2 - 22) = x2 - 2x + 1 - x2 + 4 = 2x + 5
e. (x + 2)(x2 - 2x + 4) - x(x2 + 2) = x3 + 23 - x3 - 2x = 8 - 2x
f. (x + 2y)3 - 6xy(x + 2y) = x3 + 6x2y + 12xy2 + 8y - 6x2y + 12xy2 = x2 + 24xy2 + 8y
Bài 3:
a: \(x^3+x^2-4x-4=\left(x+1\right)\left(x-2\right)\left(x+2\right)\)
b: \(x^2-4x+4-y^2=\left(x-2-y\right)\left(x-2+y\right)\)
c: \(\left(x^2+9\right)^2-36x^2=\left(x+3\right)^2\cdot\left(x-3\right)^2\)
