Rút gọn các biểu thức sau:

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

Tìm GTLN

\(a,C=5-x^2-5x\\ b,B=3-4x-x^2\\ c,C=8-x^2-5x\)

Tìm x, biết:

\(a.\left(2x-1\right)^2-\left(4x^2-1\right)=0\\ b.\left(x+2\right)^2-x\left(x-3\right)=2\\ c.\left(x-5\right)^2-x\left(x+2\right)=5\\ d.\left(x-1\right)^2+x\left(4-x\right)=11\\ e.\left(x-3\right)\left(x+3\right)=\left(x-5\right)^2\\ f.\left(2x+1\right)^2-4x\left(x-1\right)=17\\ g.\left(3x+1\right)^2-9x\left(x-2\right)=25\\ h.\left(3x-2\right)\left(3x+2\right)-9\left(x-1\right)x=0\\ i.\left(x+2\right)^2-\left(x-2\right)\left(x+2\right)=0\\ k.\left(x+2\right)^2-\left(x-3\right)\left(x+3\right)=-3\)

I think this report shows __that___ why we have to act now.