a, $\frac{2}{7}$ + $\frac{5}{7}$ = $\frac{2+5}{7}$ = $\frac{7}{7}$ = 1
b, $\frac{3}{4}$ : $\frac{6}{5}$ = $\frac{3}{4}$ . $\frac{5}{6}$ = $\frac{3.5}{4.6}$ = $\frac{15}{24}$ = $\frac{5}{8}$
c, $\frac{3}{5}$ + $\frac{4}{15}$ = $\frac{9}{15}$ + $\frac{4}{15}$ = $\frac{13}{15}$
d, $\frac{-3}{5}$ + $\frac{5}{7}$ = $\frac{-21}{35}$ + $\frac{25}{35}$ = $\frac{4}{35}$
e, $\frac{5}{6}$ : $\frac{-7}{12}$ = $\frac{5}{6}$ . $\frac{-12}{7}$ = $\frac{5.(-12)}{6.7}$ = $\frac{5.6.(-2)}{6.7}$ = $\frac{-10}{7}$
Câu 9:
a, 34 - x = -5
x = 34 - (-5)
x = 34 + 5
x = 39
Vậy x = 39
b, $\frac{5}{3}$x = $\frac{-1}{3}$
⇒ x = $\frac{-1}{3}$ : $\frac{5}{3}$
⇒ x = $\frac{-1}{3}$ . $\frac{3}{5}$
⇒ x = $\frac{-1}{5}$
Vậy x = $\frac{-1}{5}$
c, 27 + x = 58
x = 58 - 27
x = 31
Vậy x = 31
d, ( Đề sai nên chị chịu nha =))
(xin hay nhất)
Chúc em học tốt!!!
