bài 1 tính nhanh ạ, 150 -34+44-66-50 b, 125 -36+25-75
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A. 150 - 34 + 44 - 66 - 50 = (150 - 50 ) - ( 34 + 66 ) + 44 = 100 - 100 + 44 = 44
B. 125 - 36 + 25 - 74 = (125 + 25 ) - (36 + 74 ) = 150 - 110 = 40
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) \(3^x.5-15=390\)
\(3^x.5=390+15\)
\(3^x.5=405\)
\(3^x=405:5\)
\(3^x=81=3^4\)
\(\Rightarrow x=4\)
(45+75)*66+(75+45)*34
=(45+75)*(66+34)
=120*100
=12000
11+22+33+44+55+66+77+88+99:11
=11+22+33+44+55+66+77+88+9
=(11+9)+(22+88)+(33+77)+(44+66)+55
=20+110*3+55
=20+330+55
=405
Ta có :
a, (45 + 75) x 66 + (75 + 45) x 34
= (45 + 75) x (66 + 34)
= 120 x 100
= 12000
11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99 : 11
= 33 + 77 + 121 + 165 + 9
= 405
a) \(48.19+48.15+134.52\)
\(=48\left(19+15\right)+6968\)
\(=48.34+6968\)
\(=1632+6968\)
\(=8600.\)
b) \(27.121-87.27+73.34\)
\(=27\left(121-87\right)+73.34\)
\(=27.34+73.34\)
\(=34\left(27+73\right)\)
\(=34.100\)
\(=3400.\)
c) \(125.98-125.46-52-25\)
\(=125\left(98-46\right)-52-25\)
\(=125.52-52-25\)
\(=52\left(125-1\right)-25\)
\(=52.124-25\)
\(=6448-25\)
\(=6423.\)
d) \(136.23+136.17-40.36\)
\(=136\left(23+17\right)-40.36\)
\(=136.40-40.36\)
\(=40\left(136-36\right)\)
\(=40.100\)
\(=4000.\)
e) \(66.25+5.66+66.14+33.94\)
\(=33\left(2.50+5.2+14.2+94\right)\)
\(=33\left(50+10+28+94\right)\)
\(=33.182\)
\(=6006.\)
Bài 2:
a: \(17-x=3\)
=>\(x=17-3\)
=>x=14(nhận)
b: \(2\cdot\left(x-1\right):3=6\)
=>\(2\left(x-1\right)=6\cdot3=18\)
=>x-1=18/2=9
=>x=9+1=10(nhận)
c: \(x+\left(-2\right)=\left(-11\right)+7\)
=>\(x-2=-4\)
=>\(x=-4+2=-2\left(loại\right)\)
d: \(\left(x-1\right)^2-5=20\)
=>\(\left(x-1\right)^2=25\)
=>\(\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\left(nhận\right)\\x=-4\left(loại\right)\end{matrix}\right.\)
Câu 3:
a: Đặt *=a
\(\overline{57a3}⋮9\)
=>\(5+7+a+3⋮9\)
=>\(a+15⋮3\)
mà 0<=a<=9
nên a=3
=>*=a
b: \(A=123\cdot7+8+9\)
123*7 là số lẻ
9 là số lẻ
=>123*7+9 chia hết cho 2
mà 8 chia hết cho 2
nên \(A=123\cdot7+9+8⋮2\)
\(123\cdot7⋮3;9⋮3;8⋮̸3\)
=>\(A=123\cdot7+9+8⋮̸3\)
c: \(B=3\cdot5\cdot7+10^{50}\)
\(=5\cdot3\cdot7+5\cdot5^{49}\cdot2^{49}\)
\(=5\left(3\cdot7+5^{49}\cdot2^{49}\right)⋮5\)
=>B là hợp số
a, = 996 + 4 + 40 = 1000 + 40 = 1040
b, = 198 + 2 + 35 = 200 + 35 = 235
c, = ( 4 *25 )*(2 * 5)*55=100 * 10 * 55 = 55000
d, = 97*(36+64) = 97 * 100 = 9700
e, = (125+75)+(360+40)= 200 + 400 = 600
g, =10^2=100
a) 150 - 34 + 44 - 66 - 50
= (150 - 50) + (44 - 34) - 66
= 100 + 10 - 66
= 110 - 66
= 44
b) 152 - 36 + 25 - 75
= (152 - 36) + (75 - 25)
= 116 + 50
= 166
a 150-34+44-66-50=44
b 125-36+25-75=39