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a: \(61\cdot45+61\cdot23-68\cdot51\)
\(=61\left(45+23\right)-68\cdot51\)
\(=68\cdot61-68\cdot51\)
\(=68\left(61-51\right)=68\cdot10=680\)
b: \(3\cdot5^2-\left(75-4\cdot2^3\right)\)
\(=75-75+4\cdot8\)
\(=4\cdot8=32\)
c: \(36:\left\{2^2\cdot5-\left[30-\left(5-1\right)^2\right]\right\}\)
\(=\dfrac{36}{20-30+4^2}\)
\(=\dfrac{36}{-10+16}=\dfrac{36}{6}=6\)
d: \(\left(12\cdot49-3\cdot2^2\cdot7^2\right):\left(2020\cdot2021\right)\)
\(=\dfrac{\left(12\cdot49-12\cdot49\right)}{2020\cdot2021}=0\)
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a) (317+49)-117
=366-117
=249
b)867-(167+80)
=867-247
=620
c)(125.7):25
=875:25
=35
d)3000:75=40
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Bài 2:
a: A=(12,87+14,13)+(-14,7-37,3)
=27-52=-25
b: B=-1/3+2/5-2/3-3/5+1/5
=-1
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-75+(-49)+|75|+49-12
= -75-49+75+49-12
= (-75+75) +( -49+49) -12
= 0+0+(-12)
=-12
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a) 100:{250:[450−(4.53−25.4)]}100:{250:[450−(4.53−25.4)]}
=100:{250:[450−(4.125−25.4)]}=100:{250:[450−(4.125−25.4)]}
=100:{250:[450−(500−100)]}=100:{250:[450−(500−100)]}
=100:[250:(450−400)]=100:[250:(450−400)]
=100:(250:50)=100:(250:50)
=100:5=100:5
=20=20
b) 4(18−15)−(5−3).324(18−15)−(5−3).32
=4.3−2.32=4.3−2.32
=4.3−2.9=4.3−2.9
=12−18=12−18
=−6=−6
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a) − 7 8 + 5 − 12 + 3 4 = − 21 24 + − 10 24 + 18 24 = − 13 24
b) 21 49 + − 7 5 + 34 85 = 3 7 + − 7 5 + 2 5 = − 4 7
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____Ngốc cuồng BTS____:
-75+(-49)+|-75|+49-12
=-75+(-49)+75+49-12
=[-75+(-49)]+(75+49)-12
=-124+124-12
=0-12
=-12
\(-75+\left(-49\right)+|-75|+49-12=-75-49+75+49-12\)
\(=\left[\left(75-75\right)+\left(49-49\right)\right]-12=0+0-12=-12\)