Toán Lớp 6: bài 1 : tính ( tính hợp lý nếu có thể )
a) -15/16 × 8/-25
b) ( 4/5 + 1/2 ) × ( 3/13 – 8/13 )
c) ( -1/2 ) ³ × -4/3 -2 : -6/5
d) 7/19 × 8/11 + 7/19 × 3/11 + 12/9
đây tất cả là phân số mik đang cần gấp ai xong sớm thì mik đánh giá tốt
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Bài 1:
$a)$
$\frac{-15}{16}$ x $\frac{8}{-25}$
$=$ $\frac{-5 × 3}{2}$ × $\frac{1}{-5×5}$
$=$ $\frac{3}{2}$ ×$\frac{1}{5}$
$=$ $\frac{3}{10}$
$b)$
$(\frac{4}{5}$ + $\frac{1}{2})$ × $(\frac{3}{13}$-$\frac{8}{13})$
$=$ $(\frac{8}{10}$+ $\frac{5}{10})$ × $\frac{-5}{13}$
$=$ $\frac{13}{10}$ × $\frac{-5}{13}$
$=$ $\frac{-5}{10}$
$=$ $\frac{-1}{2}$
$c)$
$(-\frac{1}{2})^{3}$ × $(-\frac{4}{3})$ $-$ $2$ : $(-\frac{6}{5})$
$=$ $(-\frac{1}{8})$ × $(-\frac{4}{3})$ – $2$ × $(-\frac{5}{6})$
$=$ $\frac{1}{6}$ + $\frac{5}{3}$
$=$ $\frac{1}{6}$ + $\frac{10}{6}$
$=$ $\frac{11}{6}$
$d)$
$\frac{7}{19}$ × $\frac{8}{11}$ + $\frac{7}{19}$ × $\frac{3}{11}$ +$\frac{12}{9}$
$=$ $\frac{7}{19}$ × $(\frac{8}{11}$+ $\frac{3}{11})$ +$\frac{12}{9}$
$=$ $\frac{7}{19}$ × $1$ +$\frac{12}{9}$
$=$ $\frac{7}{19}$ +$\frac{12}{9}$
$=$ $\frac{63}{171}$ + $\frac{228}{63}$
$=$$\frac{228}{171}$
$=$ $\frac{4}{3}$