Câu `12`
\(\)`a, x -2 1/6 =1/3`
`=> x- 13/6 =1/3`
`=>x=1/3+13/6`
`=>x= 2/6 +13/6`
`=>x=15/6`
`b, x+3/4=(-3/2)^8 :(-3/2)^6`
`=> x+3/4=(-3/2)^2`
`=> x+3/4=9/4`
`=>x=9/4-3/4`
`=>x=6/4`
`=>x=3/2`
`c, 1/10 :(3/4-2x)^2=0,4`
`=> 1/10 :(3/4-2x)^2= 2/5`
`=> (3/4-2x)^2=1/10:2/5`
`=> (3/4-2x)^2=1/10 xx 5/2`
`=> (3/4-2x)^2=5/20`
`=> (3/4-2x)^2=1/4`
`=> (3/4-2x)^2=(+- 1/2)^2`
\(\Rightarrow\left[{}\begin{matrix}\dfrac{3}{4}-2x=\dfrac{1}{2}\\\dfrac{3}{4}-2x=-\dfrac{1}{2}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}2x=\dfrac{1}{4}\\2x=\dfrac{5}{4}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{1}{8}\\x=\dfrac{5}{8}\end{matrix}\right.\)
Câu `11`
`a, 9/4 + (-7)/6 *3/7`
`= 9/4 + (-21)/42`
`= 9/4 +(-1/2)`
`= 9/4 + (-2/4)`
`= 7/4`
`b, -3/8 *1/9 +1/9 *(-13)/8`
`= 1/9 * (-3/8 -13/8)`
`= 1/9 * (-16)/8`
`= 1/9 * (-2)`
`= -2/9`
`c, -1/7 +6/7 *(0,5-1/3)`
`= -1/7 +6/7 * (1/2-1/3)`
`= -1/7 +6/7 *1/6`
`=-1/7 + 6/42`
`=-1/7 +1/7`
`=0`
`d, (-1/4)^2 * 4/11 +7/11*(-1/4)^2`
`=(-1/4)^2 *(4/11+7/11)`
`=(-1/4)^2 * 11/11`
`= 1/16*1`
`=1/16`
