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Câu 3 :
\(a,\left(\left|x\right|+3\right).15-5=70\)
=>\(\left(\left|x\right|+3\right).15=70+5=75\)
=>\(\left|x\right|+3=75:15=5\)
=>\(\left|x\right|=5-3=2\)
=>\(\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)
Vậy x ∈ {2;-2}
\(b,86:\left[2.\left(2x-1\right)^2-7\right]+42=2.3^2\)
=>86:[\(2.\left(2x-1\right)^2-7\)]\(=18-42\)
=>\(2.\left(2x-1\right)^2-7=-\frac{43}{12}\)
=>\(2.\left(2x-1\right)^2=-\frac{43}{12}+7=\frac{41}{12}\)
=>\(\left(2x-1\right)^2=\frac{41}{12}:2=\frac{41}{24}\)
=>\(2x-1=\sqrt{\frac{41}{24}}=\frac{\sqrt{246}}{12}\)
=>\(2x=\frac{\sqrt{246}}{12}+1=\frac{12+\sqrt{246}}{12}\)
=>\(x=\frac{12+\sqrt{246}}{12}:2=\frac{12+\sqrt{246}}{12.2}=\frac{12+\sqrt{246}}{24}\)
Vậy \(x\in\left\{\frac{12+\sqrt{246}}{24}\right\}\)
Câu 1:
\(a,54+75-\left|-79-42\right|\)
=\(129+121\)
=\(250\)
\(b,2048-\left\{\left[39-\left(2^3.3-21\right)^2\right]:3+2017^0\right\}\)
=\(2048-\left\{\left[39-\left(8.3-21\right)^2\right]:3+1\right\}\)
=\(2048-\left\{\left[39-9\right]:3+1\right\}\)
=\(2048-\left\{30:3+1\right\}\)
=\(2048-11\)
=\(2037\)
Câu 2:
\(a,47.134-47.35+47\)
=\(47.\left(134-35+1\right)\)
=\(47.100=4700\)
\(b,-\left(-2017+2789\right)+\left(1789-2017\right)\)
=\(2017+\left(-2789\right)+1789+\left(-2017\right)\)
=\(\left(2017-2017\right)+\left(-2789+1789\right)\)
=\(0+-1000=-1000\)
Bài 1 :
a, 25 + (-42) = - ( 42 - 25 ) = - 17
b, (-17) + 5 + 8 + 17 + (-3 )
= [ (-17) + 17 ] + [ ( 5 + 8 ) + (-3) ]
= 0 + 10
= 10
c, 25. 22 - ( 15-18 ) + ( 12 - 19 + 10 )
= 25 . 4 - (-3) + 3
= 100 - [ (-3) + 3 ]
= 100 - 0
= 100
d, 120 - 35 + 29 - 242
= 85 + 29 - 242
= 114 - 242
= -128
a,\(\left(x-15\right):50+22=24\)
\(< =>\frac{\left(x-15\right)}{50}=2< =>x-15=100\)
\(< =>x=100+15=115\)
b,\(42-\left(2x+32\right)+12:2=6\)
\(< =>42-2x-32=0\)
\(< =>10-2x=0< =>x=\frac{10}{2}=5\)
Làm nốt :
c) \(134-2\left\{156-6\cdot\left[54-2\cdot\left(9+6\right)\right]\right\}\cdot x=86\)
=> 134 - 2{156 - 6 . [54 - 2 . 15]} . x = 86
=> 134 - 2{156 - 6 . [54 - 30]} . x = 86
=> 134 - 2{156 - 6. 24} . x = 86
=> 134 - 2{156 - 144} . x = 86
=> 134 - 2.12 . x = 86
=> 134 - 24 . x = 86
=> 24.x = 48
=> x = 2
Bài 2 : a) 120 : [21 - (4x - 4)] = 23.3
=> 120 : [21 - (4x - 4)] = 8.3
=> 120 : [21 - (4x - 4)] = 24
=> 21 - (4x - 4) = 5
=> 4x - 4 = 16
=> 4x = 20
=> x = 5
b) 3.[205 - (x - 9)] - 486 = 0
=> 3.[205 - (x - 9)] = 486
=> 205 - (x - 9) = 162
=> x - 9 = 205 - 162 = 43
=> x = 43 + 9 = 52
c) 204 - 2{200 - 5.[64 - 2.(11 + 6)]} . x = 4
=> 204 - 2{200 - 5.[64 - 2.17]} . x = 4
=> 204 - 2{200 - 5 .[64 - 34]}.x = 4
=> 204 - 2{200 - 5.30} . x = 4
=> 204 - 2{200 - 150}.x = 4
=> 204 - 2.50 . x = 4
=> 2.50.x = 200
=> 100.x = 200
=> x = 2
Câu 1 Tính
a) \(-54\) + 75 - \(\frac{1}{2}\) - 79 - 42\(\frac{1}{2}\)
= 21 - \(-78,5\)- 42\(\frac{1}{2}\)
= \( 99,5\) - 42\(\frac{1}{2}\)
= 57
Câu 2 Tính nhanh
a) 47 . 134 - 47 . 35 + 47
= 47 . ( 134 - 35 ) + 47
= 47 . 99 + 47
= 4653 + 47
= 4700
Câu 3:
a: =>(|x|+3)*15=75
=>|x|+3=5
=>x=2 hoặc x=-2
b: =>86:[2(2x-1)^2-7]=2*9-16=2
=>2(2x-1)^2-7=43
=>2(2x-1)^2=50
=>(2x-1)^2=25
=>2x-1=5 hoặc 2x-1=-5
=>x=-2 hoặc x=3