Question

Tính(rút gọn)

1, x^ 2 - 2x + 5 - (x - 7)(x + 2)

2,-5x(x-5)+(x-3)(x^2-7)

3, x(x^2-x-2)-(x+5)(x-1)

4, (-x+5)(x+3)+(2x-1)(x+3)

5, -4x(x+3)(x-4)-3x(x^2-x+1)

Answer 1

1: Ta có: \(x^2-2x+5-\left(x-7\right)\left(x+2\right)\)

\(=x^2-2x+5-x^2-2x+7x-14\)

\(=3x-9\)

2: Ta có: \(-5x\left(x-5\right)+\left(x-3\right)\left(x^2-7\right)\)

\(=-5x^2+25x+x^3-7x-3x^2+21\)

\(=x^3-8x^2+18x+21\)

3: Ta có: \(x\left(x^2-x-2\right)-\left(x+5\right)\left(x-1\right)\)

\(=x^3-x^2-2x-x^2-4x+5\)

\(=x^3-2x^2-6x+5\)