Tính bằng cách hợp lí nhất:
a, 7/5 + 7/2 + 8/5 + 12/13 + 1/2 + 27/13
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a) (-125) . 4
= -500
b) (-2017) . (-2016) . 0
= 0
c) (-12) . (-11)
= 132
d) (-4) . (-8) . (-25) . (-125)
= [(-4).(-25)].[(-8).(-125)]
= 100.1000
= 100000
e) (-2).(-5).(-7)
= [(-2).(-5)].(-7)
= 10.(-7)
= -70
a: \(\left(-125\right)\cdot4=-\left(125\cdot4\right)=-500\)
b: \(\left(-2017\right)\cdot\left(-2016\right)\cdot0=0\cdot2016\cdot2017=0\)
c: \(\left(-12\right)\cdot\left(-11\right)=12\cdot11=12\cdot10+12=120+12=132\)
d: \(\left(-4\right)\cdot\left(-8\right)\cdot\left(-25\right)\cdot\left(-125\right)\)
\(=4\cdot8\cdot25\cdot125\)
\(=4\cdot25\cdot8\cdot125\)
\(=100\cdot1000=100000\)
e: \(\left(-2\right)\cdot\left(-5\right)\cdot\left(-7\right)\)
\(=-7\cdot2\cdot5\)
\(=-7\cdot10=-70\)
a) \(\dfrac{\dfrac{3}{14}-\dfrac{3}{17}+\dfrac{3}{19}}{\dfrac{5}{19}+\dfrac{5}{14}-\dfrac{5}{17}}=\dfrac{3\left(\dfrac{1}{14}-\dfrac{1}{17}+\dfrac{1}{19}\right)}{5\left(\dfrac{1}{14}-\dfrac{1}{17}+\dfrac{1}{19}\right)}=\dfrac{3}{5}\)
c) \(\dfrac{\dfrac{2}{7}+\dfrac{2}{5}+\dfrac{2}{17}-\dfrac{2}{193}}{\dfrac{3}{7}+\dfrac{3}{5}+\dfrac{3}{17}-\dfrac{3}{293}}=\dfrac{2\left(\dfrac{1}{7}+\dfrac{1}{5}+\dfrac{1}{17}-\dfrac{1}{193}\right)}{3\left(\dfrac{1}{7}+\dfrac{1}{5}+\dfrac{1}{17}-\dfrac{1}{193}\right)}=\dfrac{2}{3}\)
d)
-3/11.(-22)/66.121/15
=(-3).(-22).121
11.66.15
=11
15
3/7.2/5.7/3.20.19/72
=3.2.7.20.19
7.5.3.72
=76
16
6/7.8/13+6/13.9/7-3/13.6/7
=6/7.8/13+6/7.9/13-3/13.6/7
=6/7.(8/13+9/13-3/13)
=6/7.14/13
=12/13
-1/4.152/11+68/4.(-1)/11
=152/4.(-1)/11+68/4.(-1)/11
=(-1)/11.(152/4+68/4)
=(-1)/11.220/4
=-110/22
-5/7.2/11+(-5)/7.9/11+12/7
=-5/7.2/11+-5/7.9/11+12/7
=-5/7.(2/11+9/11)+12/7
=-5/7.1+12/7
=(-5)/7+12/7
=7/7
=1
146/13-(18/7+68/13)
=146/13-18/7-68/13
=(146/13-68/13)-18/7
=78/13-18/7
=6-18/7
=42/7-18/7
=24/7
13 - 12 + 11 + 10 - 9 + 8 - 7 - 6 + 5 - 4 + 3 + 2 - 1
= 1 + 11 - 1 + 1 + 11 - 7 + 1
= 12 - 1 + 1 + 11 - 7 + 1
= 11 + 1 + 11 - 7 + 1
= 12 + 11 - 7 + 1
= 23 - 7 + 1
= 16 + 1
=17
\(\dfrac{7}{5}+\dfrac{8}{5}+\dfrac{7}{2}+\dfrac{1}{2}+\dfrac{12}{13}+\dfrac{27}{13}=\dfrac{15}{5}+\dfrac{8}{2}+\dfrac{39}{13}=3+4+3=10\)
a) \(\dfrac{7}{5}+\dfrac{7}{2}+\dfrac{8}{5}+\dfrac{12}{13}+\dfrac{1}{2}+\dfrac{27}{13}=\left(\dfrac{7}{5}+\dfrac{8}{5}\right)+\left(\dfrac{7}{2}+\dfrac{1}{2}\right)+\left(\dfrac{12}{13}+\dfrac{27}{13}\right)\)\(=3+4+3=10\)