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222-9+11+12:2*14+14 = ? ( )

## Toán Lớp 8: M=2.(1-9x^2)/3x^2+6x:2-6x/3x a)rút gọn M b) tìm x đẻ M là giá trị nguyên

Toán Lớp 8: M=2.(1-9x^2)/3x^2+6x:2-6x/3x
a)rút gọn M
b) tìm x đẻ M là giá trị nguyên

$$\begin{array}{l} a)\dfrac{{1 + 3x}}{{x + 2}}\\ b)\left[ \begin{array}{l} x = 3\\ x = – 7\\ x = – 1\\ x = – 3 \end{array} \right. \end{array}$$
$$\begin{array}{l} a)DK:x \ne \left\{ { – 2;0;\dfrac{1}{3}} \right\}\\ M = \dfrac{{2\left( {1 – 9{x^2}} \right)}}{{3{x^2} + 6x}}:\dfrac{{2 – 6x}}{{3x}}\\ = \dfrac{{2\left( {1 – 3x} \right)\left( {1 + 3x} \right)}}{{3x\left( {x + 2} \right)}}.\dfrac{{3x}}{{2\left( {1 – 3x} \right)}}\\ = \dfrac{{1 + 3x}}{{x + 2}}\\ b)M = \dfrac{{3x + 1}}{{x + 2}} = \dfrac{{3\left( {x + 2} \right) – 5}}{{x + 2}}\\ = 3 – \dfrac{5}{{x + 2}}\\ M \in Z \to \dfrac{5}{{x + 2}} \in Z\\ \to x + 2 \in U\left( 5 \right)\\ \to \left[ \begin{array}{l} x + 2 = 5\\ x + 2 = – 5\\ x + 2 = 1\\ x + 2 = – 1 \end{array} \right.\\ \to \left[ \begin{array}{l} x = 3\\ x = – 7\\ x = – 1\\ x = – 3 \end{array} \right. \end{array}$$