Question

Tính: 4(x-1)(x+5)-(x+2)(x+5)-3(x-1)(x+2)

Answer 1

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

<=> 4(x-1)(x+5)-3(x+2)(x+5)+4(x+2)(x+5)-3(x-1)(x+2)

<=> 4(x+5)(x-1+x+2)+[-3(x+2)(x+5+x-1)]

<=> 4(x+5)(2x+1)-3(x+2)(2x+2)

<=> (4x+20)(2x+1)+(-3x-6)(2x+2)

<=> 8x²+4x+40x+20-6x²-6x-12x-12

<=> 2x²+26x+8

<=> 2(x²+13x+8)

Answer 2

\(=3\left(x-1\right)\left(x+5\right)+\left(x-1\right)\left(x+5\right)\\ -\left(x-2\right)\left(x+5\right)-3\left(x-1\right)\left(x-2\right)\)

\(=3\left(x-1\right)\left[\left(x+5\right)-\left(x-2\right)\right]\\ +\left(x+5\right)\left[\left(x-1\right)-\left(x-2\right)\right]\)

\(=3\left(x-1\right)\left[x+5-x+2\right]+\left(x+5\right)\left[x-1-x+2\right]\)

\(=3.7\left(x-1\right)+\left(x+5\right)\)

\(=21x-21+x+5\)

\(=22x-16\)