Bài 1 Thực hiện phép tính sau
a) $\frac{-7}{12}$ + $\frac{11}{18}$ – $\frac{5}{9}$
b) $\frac{1}{7}$ – $\frac{8}{7}$ : 8 – 3 : $\frac{3}{4}$ . $(-2)^{3}$
c) 1,4 . $\frac{15}{49}$ – ($\frac{4}{3}$ + $\frac{2}{3}$) : 2$\frac{1}{5}$
Bài 2 Tìm x, biết
a) $\frac{11}{12}$ . x + $\frac{3}{4}$ = $\frac{-1}{6}$
b) 3 – ( $\frac{1}{6}$ – x) . $\frac{2}{3}$ = $\frac{2}{3}$
Giải thích các bước giải:
`1)`
`a,-7/12+11/18-5/9`
`=-21/36+22/36-20/36`
`=-19/36`
`b,1/7-8/7:8-3:3/4xx (-2)^3`
`=1/7-8/7xx1/8-3xx4/3xx(-8)`
`=1/7-1/7+32`
`=32`
`c,1,4xx15/49-(4/3+2/3):2 1/5`
`=3/7-2xx5/11`
`=3/7-10/11`
`=33/77-70/77`
`=-33/77`
`2)`
`a,11/12xxx+3/4=-1/6`
`<=>11/12xxx=-1/6-3/4`
`<=>11/12xxx=-2/12-9/12`
`<=>11/12xxx=-11/12`
`<=>x=-11/12:11/12`
`<=>x=-11/12xx12/11`
`<=>x=-1`
`b,3-(1/6-x)xx2/3=2/3`
`<=>3-1/6+x xx2/3=2/3`
`<=>17/6+x xx2/3=2/3`
`<=>x xx2/3=2/3-17/6`
`<=>x xx2/3=4/6-17/6`
`<=>x xx2/3=-13/6`
`<=>x=-13/6:2/3`
`<=>x=-13/6xx3/2`
`<=>x=-13/4`
Đáp án:
`text{Bài 1:}`
a) `-19/36`
b) `32`
c) `-37/77`
`text{Bài 2:}`
a) `x = -1`
b) `x = -10/3`
Giải thích các bước giải:
`text{Bài 1:}`
a) `-7/12+11/18-5/9`
`=-21/36 + 22/36 – 20/36 =-19/36`
`b,1/7-8/7 : 8 – 3 : 3/4 . (-2)^3`
`=1/7 – 8/7 . 1/8-3 . 4/3 . (-8)`
`=1/7-1/7+32 = 32`
c) `1,4 . 15/49-(4/3+2/3):2 1/5`
`=3/7-2 . 5/11 =3/7-10/11 =-37/77`
`text{Bài 2:}`
a) `11/12 . x+3/4=-1/6`
`to 11/12. x=-1/6-3/4`
`to 11/12 . x=-11/12`
`to x=-11/12:11/12`
`to x=-1`
Vậy `x = -1`
b) `3-(1/6-x) . 2/3=2/3`
`to (1/6-x) . 2/3 = 3-2/3`
`to (1/6-x) . 2/3 = 7/3`
`to 1/6-x = 7/3 : 2/3`
`to 1/6-x = 7/2`
`to x = 1/6 – 7/2`
`to x = -10/3`
Vậy `x = -10/3`