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a) 91.25 - 91.13 - 91.12 = 91.(25 - 13 - 12) = 0;
b) 47.8 - 27.9 + 47.12 - 27.11 = 47. (8 +12) - 27.(9 +11)
= (47-27).20 = 400;
c) 236 : 3 + 64 : 3 = (236 + 64) : 3 = 100;
d) 375 : 25 - 125 : 25 = (375 - 125) : 25 = 10
Lời giải:
a. $(-125)+70+(-375)+230$
$=(70+230)-(125+375)=300-500=-200$
b.
$(-8).12.25(-6)=(-8.25)(12.-6)=-200.(-72)=14400$
c.
$98.19+11.(-19)+13.19=98.19-11.19+13.19$
$=19(98-11+13)=19.100=1900$
d.
$150-[129-(25.2.3^2)^2]+1^{2023}=150-[129-49]+1=150-80+1=70+1=71$
a) 999.3
=(1000-1).3
=1000.3-1.3
=3000-3
=2997
b) 375.25
=375.(100:4)
=375.100:4
=37500:4
=9375
c)34567-29900
=34567-(30000-100)
=34567-30000+100
=4567+100
=4467
d)25000:125
=25000:(1000:8)
=25000:1000.8
=25.8
=200
1. = (-8) . 125 . (-4) . 25 . (-375)
= -1000 . (-100) . (-375)
= -37500000
2. = (-19) . (8 - 3)
= (-19) . 5
= -95
3.= (-137) . (1 + 76 + 23)
= (-137) . 100
= -13700
4. = 24.(-21 + 121)
= 24 . 100
= 2400
(-8).25.(-375).(-4).125
= [(-4).25].[(-8).125].(-375)
=(-100) . (-1000) . (-375)
= -37500000
(-19).8 + (-19) . (-3)
= (-19) .[8+(-3)]
bài này dễ mà mấy câu khác bạn tự làm đi nha
nếu không biết làm thì cứ kết bạn với mình mình giải tiếp cho
1.
a) \(125+80+375+220\)
\(=\left(125+375\right)+\left(80+220\right)\)
\(=500+300\)
\(=800\)
b) \(25.11.8.4.125\)
\(=\left(25.4\right).\left(8.125\right).11\)
\(=100.1000.11\)
\(=1100000\)
c) \(18.74+18.27-18\)
\(=18.\left(74+27-1\right)\)
\(=18.100\)
\(=1800\)
d) \(75.23+75.77-500\)
\(=75.\left(23+77\right)-500\)
\(=75.100-500\)
\(=7500-500\)
\(=7000\)
e) \(150:\left[25.\left(18-4^2\right)\right]\)
\(=150:\left[25.\left(18-16\right)\right]\)
\(=150:\left[25.2\right]\)
\(=150:50\)
\(=3\)
f) \(125.23.2.8.50\)
\(=\left(125.8\right).\left(2.50\right).23\)
\(=1000.100.23\)
\(=2300000\)
g) \(235+88+165+12\)
\(=\left(235+165\right)+\left(88+12\right)\)
\(=400+100\)
\(=500\)
h) \(71.32+71.68-1100\)
\(=71.\left(32+68\right)-1100\)
\(=71.100-1100\)
\(=7100-1100\)
\(=6000\)
i) \(6^7:6^6+4^3.2-24^0\)
\(=6+64.2-1\)
\(=6+128-1\)
\(=133\)
j) \(546-6.\left[158:\left(30+7^2\right)\right]\)
\(=546-6.\left[158:\left(30+49\right)\right]\)
\(=546-6.\left[158:79\right]\)
\(=546-6.2\)
\(=546-12\)
\(=534\)
k) \(268+147+132+253\)
\(=\left(268+132\right)+\left(147+253\right)\)
\(=400+400\)
\(=800\)
2.
a) \(7x=707\)
\(x=707:7\)
\(x=101\)
b) \(6x+5=47\)
\(6x=47-5\)
\(6x=42\)
\(x=42:6\)
\(x=7\)
c) \(35:\left(x+1\right)=7\)
\(x+1=35:7\)
\(x+1=5\)
\(x=5-1\)
\(x=4\)
d) \(12+\left(29-3x\right)=35\)
\(29-3x=35-12\)
\(29-3x=23\)
\(3x=29-23\)
\(3x=6\)
\(x=6:3\)
\(x=2\)
e) \(2.4^x+10^1=138\)
\(2.4^x=138-10\)
\(2.4^x=128\)
\(4^x=128:2\)
\(4^x=64=4^3\)
\(\Rightarrow x=3\)
f) \(7x=140\)
\(x=140:7\)
\(x=20\)
g) \(7\left(15-x\right)+14=84\)
\(7\left(15-x\right)=84-14\)
\(7\left(15-x\right)=70\)
\(15-x=70:7\)
\(15-x=10\)
\(x=15-10\)
\(x=5\)
h) \(3^x.5-15=390\)
\(3^x.5=390+15\)
\(3^x.5=405\)
\(3^x=405:5\)
\(3^x=81=3^4\)
\(\Rightarrow x=4\)
a,( 25 + 39 ) +21 = 25 + ( 39 + 21 ) = 25 + 60 =85
b,( 997+29 +3 +51)= ( 997 + 3 ) + ( 29 + 51 ) = 1000 + 80 = 1080
c. 578 + 125 + 422 + 375 = ( 578 + 422 ) + ( 125 + 375 ) = 1000 + 500 = 1500
d.915 + 85 + 117 + 23 = ( 915 + 85 ) + ( 117 + 23 ) = 1000 + 140 = 1140
a) 125 + 70 + 375 + 230 = (125 + 375) + (70 + 230) = 500 + 300 = 800
b) 62 : 4 . 3 + 2 . 52 = 62 : 22 . 3 + 2 . 25 = 32 . 3 + 50 = 33 + 50 = 27 + 50 = 77
c) 150 : [25 . (18 - 42)] = 150 : (25 . 2) = 150 : 50 = 3
375 : 25 - 125 : 25
= (375 - 125) : 25
= 250 : 25
= 10
375:25-125:25
= (375:25)-(125:25)
=15-5
=10