Question

phân tích thành nhân tử a,x²-18x-40 b,x² +18x-40 c,5x²-18x-8

Answer 1

a) \(x^2-18x-40\Leftrightarrow x^2+2x-20x-40\)

\(\Leftrightarrow x\left(x+2\right)-20\left(x+2\right)\Leftrightarrow\left(x-20\right)\left(x+2\right)\)

b) \(x^2+18-40\Leftrightarrow x^2-2x+20x-40\)

\(\Leftrightarrow x\left(x-2\right)+20\left(x-2\right)\Leftrightarrow\left(x+20\right)\left(x-2\right)\)

c) \(5x^2-18x-8\Leftrightarrow5x^2+2x-20x-8\)

\(\Leftrightarrow x\left(5x+2\right)-4\left(5x+2\right)\Leftrightarrow\left(x-4\right)\left(5x+2\right)\)