a) $\frac{5}{4}$- $\frac{1}{2}$+ $\frac{-7}{8}$
b) (-$\frac{5}{24}$+ 0.75+ $\frac{7}{12}$ : (-2$\frac{1}{8}$ )
c) Tính nhanh nếu có thể $\frac{-5}{7}$ . $\frac{2}{11}$ +$\frac{-5}{7}$ .$\frac{9}{11}$+ 1$\frac{5}{7}$
a) $\frac{5}{4}$- $\frac{1}{2}$+ $\frac{-7}{8}$
b) (-$\frac{5}{24}$+ 0.75+ $\frac{7}{12}$ : (-2$\frac{1}{8}$ )
c) Tính nhanh nếu có thể $\frac{-5}{7}$ . $\frac{2}{11}$ +$\frac{-5}{7}$ .$\frac{9}{11}$+ 1$\frac{5}{7}$
Đáp án:
A) 5/4-1/2+-7/8
=10/8-4/8+-7/8
=6/8+-7/8
=-1/8
B) (-5/14) + 0,75+7/12:(-17/8)
=(-5/14)+0,75+7/12.(-8/17)
=(-5/14)+0,75+(-14/51)
=(-5/14)+3/4+(-14/51)
=(-10/28)+12/28+(-14/51)
=2/28+(-14/51)
=1/14+(-14/51)
=51/714+(-196/714)
=-145/714
c) -5/7.(2/11+9/11).1.5/7
=-5/7.1.5/7
=0
Đáp án:
a)$\frac{5}{4}$ – $\frac{1}{2}$+ $\frac{-7}{8}$
=$\frac{5×2}{4×2}$- $\frac{1×4}{2×4}$ + $\frac{-7}{8}$
= $\frac{10}{8}$ – $\frac{4}{8} + $\frac{-7}{8}$
= $\frac{-1}{8}$
b(-$\frac{5}{24}$ + 0,75 + $\frac{7}{12}$): ( -2$\frac{1}{8}$)
= (-$\frac{5}{24}$ +$\frac{3.6}{4.6}$ + $\frac{7.2}{12.2}$) : $\frac{-15.3}{8.3}$
=(-$\frac{5}{24}$ + $\frac{18}{24}$ + $\frac{14}{24}$) : $\frac{-45}{24}$
=$\frac{9}{8}$ : $\frac{-45}{24}$
= -$\frac{3}{5}$
c)$\frac{-5}{7}$ . $\frac{2}{11}$+ $\frac{-5}{7}$. $\frac{9}{11}$+1.$\frac{5}{7}$
=$\frac{-5}{7}$.($\frac{2}{11}$ + $\frac{9}{11}$) + $\frac{5}{7}$
= $\frac{-5}{7}$ . 1 +$\frac{5}{7}$
= 0
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