tính nhanh
a,99 x 57
b,998x 64
c,7593-1197
d,27x332+68x27+73x332+68x73
e,43x11
g,267x101
f,425x1001
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Giải :
a) 997 + 86 = 997 + ( 3 + 83 ) = ( 997 + 3 ) + 83 = 100 + 83 = 1083
b) 37 x 38 + 62 x 37 = 37 x ( 38 + 62 ) = 37 x 100 = 3700
c) 27 x 332 + 68 x 27 + 73 x 332 + 68 x 73
= 332 x ( 27 + 73 ) + 68 x ( 27 + 73 )
= 332 x 100 + 68 x 100
= 100 x ( 332 + 68 )
= 100 x 400
= 40 000
d) 43 x 11 = 43 x ( 10 + 1 ) = 430 + 43 = 473
67 x 101 = 67 x ( 100 + 1 ) = 6700 + 67 = 6767
423 x 1001 = 423 x ( 1000 + 1 ) = 423000 + 423 = 423423
a) 997 + 86 = 1083
b) 37 x 38 + 62 x 37 = 37 x (38 + 62)
= 37 x 100
= 3700
c)27 x 332 + 68 x 27 + 73 x 332 + 68 x 73 = 27 x (332 + 68) + 73 x (332 + 68)
= 27 x 400 + 73 x 400
= (27 + 73) x 400
= 100 x 400
= 40000
d) 43 x 11 = 473 ; 67 x 101 = 6767 ; 423 x 1001 = 423423
chúc bạn học tốt
\(a,=\dfrac{1}{3}\times\left(\dfrac{1}{2}+\dfrac{1}{3}\right)=\dfrac{1}{3}\times\dfrac{5}{6}=\dfrac{5}{18}\\ b,=\dfrac{4}{5}\times\left(\dfrac{1}{2}-\dfrac{1}{3}\right)=\dfrac{4}{5}\times\dfrac{1}{6}=\dfrac{2}{15}\\ c,=456\times99-6\times99+456\\ =456\times\left(99+1\right)-594\\ =456\times100-594=45600-594=45006\\ d,=101\times\left(101-1\right)=101\times100=10100\)
Lời giải:
$A=(99-97)+(95-93)+(91-89)+...+(7-5)+(8-1)$
$=\underbrace{2+2+2+...+2}_{24}+7$
$=2\times 24+7$
$=55$
Ta có: 99–97 +95–93+...+7–5+3−1
=(99−97)+(95−93)+...+(7−5)+(3−1)
=2+2+...+2+2 (có 25 số 2)
=2.25
=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) \(3457-27\times48-48\times73+6543\)
\(=\left(3457+6543\right)-48\times\left(27+73\right)\)
\(=10000-48\times100\)
\(=10000-4800\)
\(=5200\)
B1:
\(a.301^2=\left(300+1\right)^2=300^2+2.300.1+1^2\\ =90000+600+1=90601\\ b.88^2+2.88.12+12^2=\left(88+12\right)^2=100^2=10000\\ c.99.100=100^2-100=10000-100=9900\\ d,153^2+94.153+47^2=153^2+2.153.47+47^2=\left(153+47\right)^2=200^2=40000\)
B2:
\(A=x^2-20x+101\\ =x^2-2.x.10+10^2+1\\ =\left(x-10\right)^2+1\ge1\forall x\in R\left(Vì:\left(x-10\right)^2\ge0\forall x\in R\right)\\ \Rightarrow min_A=1\Leftrightarrow x-10=0\Leftrightarrow x=10\)
1. \(\left(\dfrac{1}{99}+\dfrac{12}{999}-\dfrac{123}{9999}\right).\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)\)
\(=\left(\dfrac{1}{99}+\dfrac{12}{999}-\dfrac{123}{9999}\right).0\)
\(=0\)
a,b,c,e,g,f tính máy tính nha
a =5643
b =63872
c = 6396
d= 4349200
e=473
g=26967
f=425425