Bài1 : Rút gọn a) 78/-26 b) 9.12/(-60).8 c) 5^73 . 4^2 / 5^74.(-4)^3 d) x^3-9^2/x^4.y Bài 2 : Tìm x , biết a) x-7/5=6/-10 b) x-1/5=x+1/4 Chú thích : / = phần nhanh với ạ , mik cần gấp

Bài `1.`

`a)` $\dfrac{78}{-26}$ $=-\dfrac{78}{26}$ $=-3$

`b)` $\dfrac{9 . 12}{\left(-60\right) . 8}$ $=\dfrac{9 . 12}{-12 . 5 . 8}$ $=\dfrac{9}{-5 . 8}$ $=-\dfrac{9}{40}$

`c)` $\dfrac{\:5^{73}. 4^2}{5^{74}.\left(-4\right)^3}$ $=\dfrac{4^2}{5\left(-4\right)^3}$ $=\dfrac{4^2}{-5.4^3}$ $=\dfrac{1}{-5.4}$ $=-\dfrac{1}{20}$

`d)` $\dfrac{\:x^3-9^2}{x^4\cdot \:y}$ $=\dfrac{x^3-81}{x^4y}$ 

Bài `2.`

`a)` $\dfrac{x-7}{5}=\dfrac{6}{-10}$

$\dfrac{x-7}{5}=-\dfrac{3}{5}$

$x−7=-\dfrac{3}{5}\cdot 5$

$x-7=-3$

$x=−3+7$

$x=4$

`Vậy` $x=4$

`b)` $\dfrac{x-1}{5}=\dfrac{x+1}{4}$

$4\left(x−1\right)=5\left(x+1\right)$

$4x-4=5x+5$

$−4=5x+5−4x$

$−4=x+5$

$x+5=-4$

$x=-4-5$

$x=-9$

`Vậy` $x=-9$