\(\left(27x+6\right):3-11=9\\ \left(27x+6\right):3=20\\ \left(27x+6\right)=20\times3\\ 27x+6=60\\ 27x=54\\ x=2\)

 Câu a dùng dấu tương đương trc phương trình

Câu b dùng ngoặc vuông thay cho ngoặc nhọn!

\(a)34+11x=155\\<=>11x=155-34\\<=>11x=121\\<=>x=11\)

\(x^3+6x^2+12x+8\\=(x+2)^3\\Thay.x=3.Ta có:\\(3+2)^3=5^3=125\)

\(\sqrt{4x^2-20x+25}+2x=5\\ < =>\sqrt{\left(2x-5\right)^2}+2x=5\\ < =>\left|2x-5\right|+2x=5 \\ < =>\left[{}\begin{matrix}2x-5+2x=5\left(x\ge\dfrac{5}{2}\right)\\2x-5+2x=-5\left(x< \dfrac{5}{3}\right)\end{matrix}\right.< =>\left[{}\begin{matrix}4x=10< =>x=\dfrac{5}{2}\left(tmdk\right)\\4x=0< =>x=0\left(ktmdk\right)\end{matrix}\right.\\ =>x=\dfrac{5}{2}\)

\(x(x^2y-xy^2)=x^3y-x^2y^2\)