Question

tính nhanh:

A = (2x-1)(x²+x -1) - (x-5)² - 2(x-1)(x²-x+1) - 7(x-2)

Answer 1

\(A=\left(2x-1\right)\left(x^2+x-1\right)-\left(x-5\right)^2-2\left(x-1\right)\left(x^2-x+1\right)-7\left(x-2\right)\)

\(\Leftrightarrow A=\left(2x^3+2x^2-2x-x^2-x+1\right)-\left(x^2-10x+25\right)-2\left(x^3-x^2+x-x^2+x-1\right)-\left(7x-14\right)\)

\(\Leftrightarrow A=2x^3+2x^2-2x-x^2-x+1-x^2+10x-25-2x^3+2x^2-2x+2x^2-2x+2-7x+14\)

\(\Leftrightarrow A=2x^3+2x^2-2x-x^2-x+1-x^2+10x-25-2x^3+2x^2-2x+2x^2-2x+2-7x+14\)

\(\Leftrightarrow A=4x^2-4x-8\)