1.Thực hiện phép tính
a)-(-25)-18+(+32)
b)-(-10)-(5+11-7)
2.Tính một cách hợp lí
a)35-(-47)-49+(-47)-(+35)
b)-(81-32-47)+81-(32+2)
3.Tìm số nguyên x, biết:
a)-36-2x=-12
b)48:(1+x)=-2 mũ 2
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a) \(6^2:4\times3+2\times5^2\)
\(=36:4\times3+2\times25\)
\(=9\times3+50\)
\(=27+50\)
\(=77\)
b) \(125+70+375+230\)
\(=\left(125+375\right)+\left(70+230\right)\)
\(=500+300\)
\(=800\)
c) \(150:\left[25\times\left(18-4^2\right)\right]\)
\(=150:\left[25\times\left(18-16\right)\right]\)
\(=150:\left[25\times2\right]\)
\(=150:50\)
\(=3\)
a) \(31\cdot72+\left(-31\right)\cdot70-2\cdot70\)
\(=31\cdot72-31\cdot70-2\cdot70\)
\(=31\cdot\left(72-70\right)-2\cdot70\)
\(=31\cdot2-2\cdot70\)
\(=2\cdot\left(31-70\right)\)
\(=2\cdot-39\)
\(=-78\)
b) \(25\cdot\left(32+17\right)-32\cdot\left(25+47\right)\)
\(=25\cdot32+25\cdot17-32\cdot25-32\cdot47\)
\(=25\cdot\left(32-32+17\right)-32\cdot47\)
\(=25\cdot17-32\cdot47\)
\(=425-1504\)
\(=-1079\)
\(\left(\frac{9}{25}-2.18\right):\left(3\frac{4}{5}-0,2\right)\)
= -1,82:4=-0,455
Bài 2: Tính nhanh
a) 29 + 132 + 237 + 868 + 3
= 29+(132+858)+(237+3)
=29+990+240
=1259
a) (-25). ( 35-147) + 35. (25-147)
= -875 + 3675 + 875 - 5145
= ( -875 + 875 ) + 3675 - 5145
= 0 + ( - 1470 )
= - 1475
(\(\dfrac{9}{25}\) - 2.18) : (\(\dfrac{19}{5}\) + 0,2)
=(\(\dfrac{9}{25}\) - 2.18) : (\(\dfrac{19}{5}\) +\(\dfrac{1}{5}\) )
=(\(\dfrac{9}{25}\)- 36) : 4
=\(\dfrac{-117}{5}\) : 4
= \(\dfrac{-117}{20}\)
(\(\dfrac{9}{25}\)-2.18) : (\(\dfrac{19}{5}\) +0,2)
= (\(\dfrac{9}{25}\)- 2.18) : (\(\dfrac{19}{5}\)+\(\dfrac{1}{5}\))
= (\(\dfrac{9}{25}\)-36): 4
= \(\dfrac{-891}{25}\):4
=\(\dfrac{-891}{100}\)
= (8.125). (25.4).33
= 1000. 100.9
= 100 000.9
= 900 000
Bài 1:
a: \(-\left(-25\right)-18+\left(+32\right)\)
=25-18+32
=7+32
=39
b: \(-\left(-10\right)-\left(5+11-7\right)\)
\(=10-\left(16-7\right)\)
=10-9=1
Bài 2:
a: 35-(-47)-49+(-47)-(+35)
=(35-35)+(47-47)+(-49)
=0+0+(-49)
=-49
b: -(81-32-47)+81-(32+2)
=-81+32+47+81-32-2
=(-81+81)+(32-32)+(47-2)
=0+0+45
=45
Bài 3:
a: -36-2x=-12
=>2x+36=12
=>2x=12-36=-24
=>\(x=-\dfrac{24}{2}=-12\)
b: \(48:\left(x+1\right)=-2^2\)
=>\(\dfrac{48}{x+1}=-4\)
=>\(x+1=-\dfrac{48}{4}=-12\)
=>x=-12-1=-13
Bài 1:
a)-(-25)-18+(+32)
=25-18+32
=7+32
=39
b)-(-10)-(5+11-7)
=10-5-11+7
=5-11+7
=(-6)+7
=1