Question

bài 1 : phân tích đa thúc sau thành nhân tử chung

a) 2x²  - 7x  + 3

b) x² - 6x + 5

c) 5x(x-2y) + 2(2y-x)²

d) 7x(y-4)² - (4-y)³

Answer 1

a) 2x²-6x-x+3 = 2x(x-3) - (x-3) = (x-3)(2x-1)

b) x²-x-5x+5 = x(x-1) - 5(x-1) = (x-1)(x-5)

c) 5x(x-2y) + 2( x-2y)² = (x-2y)(5x+2x-2y) = (x-2y)(7x-2y)

chú ý : (A-B)²=(B-A)²

d) 7x(4-y)² - (4-y)³ = ( 16-8y+y²) (7x-4+y)

Answer 2

a) \(2x^2-7x+3=2x^2-6x-x+3=2x\left(x-3\right)-\left(x-3\right)=\left(x-3\right)\left(2x-1\right)\)

b) \(x^2-6x+5=x^2-5x-x+5=x\left(x-5\right)-\left(x-5\right)=\left(x-5\right)\left(x-1\right)\)

c)\(5x\left(x-2y\right)+2\left(2y-x\right)^2=5x\left(x-2y\right)+2\left(x-2y\right)^2\\ =\left(x-2y\right)\left(5x+2x-4y\right)=\left(x-2y\right)\left(7x-4y\right)\)

d) \(7x\left(y-4\right)^2-\left(4-y\right)^3=7x\left(y-4\right)+\left(y-4\right)^3=\left(y-4\right)\left(7x-y-4\right)\)