Question

Giúp mình 3 câu này với

a) 3(x - y) - 5x(y - x)
b) 7x² - 6x - y² + 9
c) 5x² - 5xy - 10x + 10y

Answer 1

a) \(=\left(x-y\right)\left(3+5x\right)\)

b) \(=\left(x^2-6x+9\right)-y^2=\left(x-3\right)^2-y^2=\left(x-y-3\right)\left(x+y-3\right)\)

c) \(=5\left(x^2-xy-2x+2y\right)=5\left[x\left(x-y\right)-2\left(x-y\right)\right]=5\left(x-y\right)\left(x-2\right)\)