Câu hỏi của Minh Thuy Bui

Question

$\dfrac{1}{3x-2}-\dfrac{1}{3x+2}-\dfrac{3x-6}{4-9x^2}$Thực hiện phép tính

iamRinz · Accepted Answer

$đk:\left\{{}\begin{matrix}3x-2\ne0\3x+2\ne0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x\ne\dfrac{2}{3}\x\ne-\dfrac{2}{3}\end{matrix}\right.$$\dfrac{1}{3x-2}-\dfrac{1}{3x+2}-\dfrac{3x-6}{4-9x^2}\
=\dfrac{1}{3x-2}-\dfrac{1}{3x+2}+\dfrac{3x-6}{9x^2-4}\
=\dfrac{3x+2-\left(3x-2\right)+3x-6}{9x^2-4}\
=\dfrac{3x+2-3x+2+3x-6}{9x^2-4}\
=\dfrac{3x-2}{\left(3x-2\right)\left(3x+2\right)}\
=\dfrac{1}{3x+2}$Câu trả lời: $đk:\left\{{}\begin{matrix}3x-2\ne0\3x+2\ne0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x\ne\dfrac{2}{3}\x\ne-\dfrac{2}{3}\end{matrix}\right.$$\dfrac{1}{3x-2}-\dfrac{1}{3x+2}-\dfrac{3x-6}{4-9x^2}\
=\dfrac{1}{3x-2}-\dfrac{1}{3x+2}+\dfrac{3x-6}{9x^2-4}\
=\dfrac{3x+2-\left(3x-2\right)+3x-6}{9x^2-4}\
=\dfrac{3x+2-3x+2+3x-6}{9x^2-4}\
=\dfrac{3x-2}{\left(3x-2\right)\left(3x+2\right)}\
=\dfrac{1}{3x+2}$

Khoá học trên OLM (olm.vn)

Khoá học trên OLM (olm.vn)