Thực hiện phép tính
a) [ 12,(1) - 2,3(6)]: 4,(21)
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a, ( - 7 ) x ( - 8 ) = 56
b, 3 / 7 x ( - 2 / 9 ) = - 6 / 63 = - 2 / 21
c, - 7 / 6 : 7 / 12 = - 7 / 6 x 12 / 7 = - 12 / 6 = -2
d, - 1 / 2 x 3 / 4 + 1 / 4 x ( - 1 / 2 ) = - 1 / 2 x ( 3 / 4 + 1 / 4 ) = - 1 / 2 x 1 = - 1 / 2
c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)
\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)
\(=1-2=-1\)
Giải:
a)-1/12+4/3=-1/12+16/12=15/12=5/4
b)(-4/14-3/15)-(1/5-20/35-(-1)).7
=-17/35-22/35.7
=-17/35-22/5
=-171/35
c)3/5+-5/20+30/75+-7/4
=3/5+-1/4+2/5+-7/4
=(3/5+2/5)+(-1/4+-7/4)
=1+-2
=-1
d)5/6.-12/14+7/13
=-5/7+7/13
=-16/91
e)2/-9-5/-36-1/4
=-1/12-1/4
=-1/3
f)2/23+-5/12+7/18+21/23+-7/12
=(2/23+21/23)+(-5/12+-7/12)+7/18
=1+-1+7/18
=7/18
\(a,\dfrac{15^3}{5^4}\)
\(=\dfrac{\left(3\cdot5\right)^3}{5^4}\)
\(=\dfrac{3^3\cdot5^3}{5^4}\)
\(=\dfrac{3^3}{5}\)
\(=\dfrac{27}{5}\)
\(---\)
\(b,\dfrac{21^3}{7^4}\)
\(=\dfrac{\left(3\cdot7\right)^3}{7^4}\)
\(=\dfrac{3^3\cdot7^3}{7^4}\)
\(=\dfrac{3^3}{7}\)
\(=\dfrac{27}{7}\)
\(---\)
\(c,\dfrac{6^6}{3^8}\)
\(=\dfrac{\left(2\cdot3\right)^6}{3^8}\)
\(=\dfrac{2^6\cdot3^6}{3^8}\)
\(=\dfrac{2^6}{3^2}\)
\(=\dfrac{64}{9}\)
#\(Toru\)
a) 42x99-21x176-35x12
=4158-3696-420
=42
b){[213^0+(999-998)^324]x2-12x5}-4^9:4^6
={[1+1^324]x2-60}-4^3
={[1+1]x2-60}-64
={2x2-60}-64
={4-60}-64
=-56-64
=-120
c)|-27|+(-25)-(-13)
=27+(-25)+13
=2+13
=15
a, -7/2 + 3/4 - 17/2 = (-7/2 - 17/2) + 3/4 = -12 + 3/4 = -45/4 = -12,75.
b, -1/12 - 21/8 + 1/3 = -1/12 + 1/3 - 21/8 = 1/4 - 21/8 = -19/8 = -2,375
=(109/9-71/30):139/33
=877/90*33/139
\(\simeq2,31\)