Question

Phân tích thành nhân tử:

a.\(30x-25-9x^2\)

b.\(2x^2-98\)

Answer 1

a) \(30x-25-9x^2=-9x^2+15x+15x-25\)

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

\(=-\left(3x-5\right)\left(3x-5\right)=-\left(3x-5\right)^2\)

b) \(2x^2-98=2\left(x^2-49\right)=2\left(x-7\right)\left(x+7\right)\)

Answer 2

\(a,30x-25-9x^2\)

\(=\left(-9x^2+15x\right)+\left(15x-25\right)\)

\(=-9x\left(x-\dfrac{5}{3}\right)+15\left(x-\dfrac{5}{3}\right)\)

\(=\left(x-\dfrac{5}{3}\right)\left(15-9x\right)\)

\(b,2x^2-98=2\left(x^2-49\right)=2\left(x+7\right)\left(x-7\right)\)