Trắc nghiệm:
Câu 1: A
Câu 2: C
Câu 3: C
Câu 4: C
Tự luận:
Câu 1:
a) $\frac{-5}{9}$ . $\frac{13}{28}$ - $\frac{13}{28}$ . $\frac{4}{9}$
= $\frac{13}{28}$ . ( $\frac{-5}{9}$ - $\frac{4}{9}$ )
= $\frac{13}{28}$ . -1
= $\frac{-13}{28}$
Câu 2:
a) $\frac{-5}{6}$ . x = $\frac{7}{12}$ + $\frac{-1}{3}$
$\frac{-5}{6}$ . x = $\frac{1}{4}$
x = $\frac{1}{4}$ : $\frac{-5}{6}$
x = $\frac{-3}{10}$
b) | 2x - $\frac{3}{4}$ | . $\frac{3}{8}$ = $\frac{1}{2}$
| 2x - $\frac{3}{4}$ | = $\frac{1}{2}$ : $\frac{3}{8}$
| 2x - $\frac{3}{4}$ | = $\frac{4}{3}$
⇒ TH1: 2x - $\frac{3}{4}$ = $\frac{4}{3}$
TH2: 2x - $\frac{3}{4}$ = $\frac{-4}{3}$
*TH1: 2x - $\frac{3}{4}$ = $\frac{4}{3}$
2x = $\frac{4}{3}$ + $\frac{3}{4}$
2x = $\frac{7}{12}$
x = $\frac{7}{12}$ : 2
x = $\frac{7}{24}$
*TH2: 2x - $\frac{3}{4}$ = $\frac{-4}{3}$
2x = $\frac{-4}{3}$ + $\frac{3}{4}$
2x = $\frac{-7}{12}$
x = $\frac{-7}{12}$ : 2
x = $\frac{-7}{24}$
Vậy x = $\frac{7}{24}$; x = $\frac{-7}{24}$
c) $\frac{2}{3}$x + $\frac{1}{6}$x = -3$\frac{5}{6}$
($\frac{2}{3}$+$\frac{1}{6}$)x = $\frac{-23}{6}$
$\frac{5}{6}$x = $\frac{-23}{6}$
x = $\frac{-23}{6}$ : $\frac{5}{6}$
x = $\frac{-23}{5}$
