Rút gọn biểu thức sau:
1/ \(\left(x-1\right)^3+\left(2-x\right)\left(4+2x+x^2\right)\)
2/ \(\left(2x-1\right)\left(4x^2+2x+1\right)-8x\left(x^2+1\right)-5\)
3/ \(5x\left(x-3\right)^2-5\left(x-1\right)^2+15\left(x+4\right)\left(x-4\right)\)
4/ \(\left(x^2+2\right)^2-\left(x+2\right)\left(x-2\right)\left(x^2+4\right)\)
5/ \(\left(m+2\right)\left(m-2\right)-\dfrac{1}{2}\left(6-8m\right)^2+17\)
1: \(=x^3-3x^2+3x-1+8-x^3=-3x^2+3x+7\)
2: \(=8x^3-1-8x^3-8x-5=-8x-6\)
3: \(=5x\left(x^2-6x+9\right)-5\left(x^2-2x+1\right)+15x^2-240\)
\(=5x^3-30x^2+45x-5x^2+10x-5+15x^2-240\)
\(=5x^3-20x^2+55x-245\)
4: \(=x^4+4x^2+4-\left(x^2-4\right)\left(x^2+4\right)\)
\(=x^4+4x^2+4-x^4+16=4x^2+20\)
