Question

1.rút gọn biểu thức

Q=\(\sqrt{4\left(1+6x+9x^2\right)}\)

2.Tìm x biết

\(3^{3x-2}=81\)

Answer 1

1.

Q=\(\sqrt{4\left(1+6x+9x^2\right)}=\sqrt{2^2.\left[1^2+2.1.3x+\left(3x\right)^2\right]}=2\sqrt{\left(1+3x\right)^2}=2.\left|3x+1\right|\left(1\right)\)

Nếu \(x\ge-\frac{1}{3}\) thì (1)\(=2\left(3x+1\right)=6x+2\)

Nếu x<\(-\frac{1}{3}\) thì (1)=\(2\left(-3x-1\right)=-6x-2\)

2.

\(3^{3x-2}=81\Leftrightarrow3^{3x-2}=3^4\Leftrightarrow3x-2=4\Leftrightarrow3x=6\Leftrightarrow x=2\)

Vậy S={2}