Tính nhanh
a) 81 2 b) 102 2 ;
c) 97.103; d) 249.351.
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a, A = ( 2007 - 1969 )
= (2000 - 1969) + 7
= 31 + 7 = 38
b, 5689 - ( x - 2008 )
= 5989 - x + 2008
Có 1 vế sao tính??
c, 475 : 5 + 120 : 5 - 195 : 5
= (475 + 120 - 195):5
= 400:5=80
d, 432 : 6 - 234 : 6 + 102 : 6
= (432 + 102 - 234):6
= 300:6
=50
a) \(\left(145\times99+145\right)-\left(143\times102-143\right)\)
\(=\left[145\times\left(99+1\right)\right]-\left[143\times\left(102-1\right)\right]\)
\(=\left(145\times100\right)-\left(143\times101\right)\)
\(=14500-14443\)
\(=57\)
b) \(54\times47-47\times53-20-27\)
\(=47\times\left(54-53\right)-20-27\)
\(=47-20-27\)
\(=0\)
c) \(10000-47\times72-47\times28\)
\(=10000-47\times\left(72+28\right)\)
\(=10000-47\times100\)
\(=10000-4700\)
\(=5300\)
d) \(3457-27\times48-48\times73+6543\)
\(=\left(3457+6543\right)-48\times\left(27+73\right)\)
\(=10000-48\times100\)
\(=10000-4800\)
\(=5200\)
a: \(68^2+64\cdot68+32^2\)
\(=\left(68+32\right)^2\)
=10000
b: \(51\cdot49=50^2-1=2499\)
a: \(32684+41325+316+675\)
\(=\left(32684+316\right)+\left(41325+675\right)\)
\(=33000+42000=75000\)
b: \(25\cdot18\cdot4\cdot2\)
\(=18\cdot2\cdot\left(25\cdot4\right)\)
\(=36\cdot100=3600\)
c: \(19\cdot81+19+18\cdot19\)
\(=19\left(81+1+18\right)\)
\(=19\cdot100=1900\)
A, 32684 + 41325 + 316 + 675
=(32684+316)+(41325+675)
=33000+42000
=75000
B, 25 x 18 x 4 x 2
=(25x4)x(18x2)
=100x36
=3600
C, 19 x 81 + 19 + 18 x 19
=19x(81+18+1)
=19x100
=1900
\(a,=72\cdot\left(-200\right)=-14400\\ b,=\left(125\cdot8\right)\left[\left(-5\right)\left(-20\right)\right]=1000\cdot100=1000000\)
\(a,2017\times\left(8+2\right)=2017\times10=20170\\ b,=\dfrac{3}{7}\times\left(\dfrac{9}{7}-\dfrac{2}{7}\right)=\dfrac{3}{7}\times1=\dfrac{3}{7}\)
Bài 2:
a: =>x-35=-23
=>x=12
b: =>|x-8|=13
=>x-8=13 hoặc x-8=-13
=>x=21 hoặc x=-5
Bài 1:
a: =42-98-42+12-12=-98
b: =10x4x3x(-25)=40x(-25)x3=-1000x3=-3000
Tính nhanh
a) 72. (-50).(-2).(-2)
b) 125.(-5).(-20).8
c) 125.(-3).(-32).(-4)
d) (-123 – 123-123-123).125
a) 6561. b) 10404. c) 9991. d) 87399.