Question

1. Phân tích đa thức thành nhân tử

a, 1/4x^2-5xy+25y^2

b, (7x-4)^2-(2x+1)^2

c, (x-2)^2-4y

d, 125-x^6

Answer 1

a) \(\frac{1}{4}x^2-5xy+25y^2=\left(\frac{1}{2}x\right)^2-5xy+\left(5y\right)^2\)

\(=\left(\frac{1}{2}x-5y\right)^2\)

b) \(\left(7x-4\right)^2-\left(2x+1\right)^2\)

\(=\left(7x-4+2x+1\right)\times\left(7x-4-2x-1\right)=\left(9x-3\right)\times\left(5x-5\right)\)

\(=3\times5\times\left(3x-1\right)\times\left(x-1\right)=15\times\left(3x-1\right)\times\left(x-1\right)\)

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

d) \(125-x^6=5^3-\left(x^2\right)^3=\left(5-x^2\right)\left(25+5x^2+x^4\right)\)