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a,
128-3x-12=23
3x=128-12-23
3x=93
x=93:3
= 31
b,
(12x+84+55):5=35
12x+84+55=35.5
12x+84+55=175
12x=175-55-84
12x=36
x=36:12
x=3
a: \(\Leftrightarrow3x+7\in\left\{1;-1;3;-3;11;-11;33;-33\right\}\)
hay \(x=-6\)
b: \(\Leftrightarrow3x-1\in\left\{1;-1;7;-7\right\}\)
hay \(x\in\left\{0;-2\right\}\)
a: \(x+7⋮x+2\)
=>\(x+2+5⋮x+2\)
=>\(5⋮x+2\)
=>\(x+2\in\left\{1;-1;5;-5\right\}\)
=>\(x\in\left\{-1;-3;3;-7\right\}\)
b: \(2x+5⋮x+1\)
=>\(2x+2+3⋮x+1\)
=>\(3⋮x+1\)
=>\(x+1\in\left\{1;-1;3;-3\right\}\)
=>\(x\in\left\{0;-2;2;-4\right\}\)
c: \(3x-2⋮x+3\)
=>\(3x+9-11⋮x+3\)
=>\(-11⋮x+3\)
=>\(x+3\in\left\{1;-1;11;-11\right\}\)
=>\(x\in\left\{-2;-4;8;-14\right\}\)
d: \(12x+1⋮3x+2\)
=>\(12x+8-7⋮3x+2\)
=>\(-7⋮3x+2\)
=>\(3x+2\in\left\{1;-1;7;-7\right\}\)
=>\(3x\in\left\{-1;-3;5;-9\right\}\)
=>\(x\in\left\{-\dfrac{1}{3};-1;\dfrac{5}{3};-3\right\}\)
e: \(x^2+3x+5⋮x+3\)
=>\(x\left(x+3\right)+5⋮x+3\)
=>\(5⋮x+3\)
=>\(x+3\in\left\{1;-1;5;-5\right\}\)
=>\(x\in\left\{-2;-4;2;-8\right\}\)
f: \(x^2-2x+3⋮x+2\)
=>\(x^2+2x-4x-8+11⋮x+2\)
=>\(11⋮x+2\)
=>\(x+2\in\left\{1;-1;11;-11\right\}\)
=>\(x\in\left\{-1;-3;9;-13\right\}\)
A.35 x 34 + 35 x 38 + 65 x 75 + 65 x 45
Câu này không tính hợp lí được
B. 12x 53 + 53 x 172 - 53 x 84
= 53 x (12 + 172 - 84)
= 53 x 100
= 5300
C. 36 x 28 + 36 x 82 + 64 x 69 + 64 x 41
= 36 x (28+82) + 64 x (69+41)
= 36 x 110 + 64 x 110
= (36+64) x 110
= 100 x 110
= 11 000
D. A = 1+2+3+...+100
= (1+ 100) x 50
= 101 x 50
= 5050
E. B =17+19+...+101+103
= (103 +17) x [(103 - 17):2 + 1]
= 120 x 44
=5280
G. D= 3x (12+13+14+15) + 3x(8+7+6+5)
= 3 x (5+6+7+8+12+13+14+15)
= 3 x (20 x 4)
= 3 x 80
=240
\(\left(12x-4^3\right).8^3=4.8^4\)
\(12x-4^3=4.8^4:8^3\)
\(12x-64=4.8\)
\(12x-64=32\)
\(12x=32+64=96\)
\(x=96:12=8\)
Vậy x=8
\(b.\left(\left(4x+28\right).3+55\right):5=35\)
\(\left(4x+28\right).3+55=35\times5\)
\(\left(4x+28\right).3+55=175\)
\(\left(4x+28\right).3=175-55\)
\(\left(4x+28\right).3=120\)
\(4x+28=120:3=40\)
\(4x=40-28=12\)
\(x=12:4=3\)
Vậy x=3
\(c.720:\left(41-\left(2x-5\right)\right)=2^3.5\)
\(720:\left(41-\left(2x-5\right)\right)=40\)
\(41-\left(2x-5\right)=720:40=18\)
\(2x-5=41-18=23\)
\(2x=23+5=28\)
\(x=28:2=14\)
Vậy x=14
\(d.\left(3x-2^4\right).7^3=2.7^4\)
\(\left(3x-16\right).7^3=2.7^4\)
\(3x-16=2.7^4:7^3\)
\(3x-16=2.7=14\)
\(3x=14+16=30\)
\(x=30:3=10\)
Vậy x=10
Nhớ k cho mình nhé! Thank you!!!
\(-7\left(3x-5\right)+2\left(7x-14\right)=28\\ -21x+35+14x-28=28\\ -7x+7=28\\ -7x=21\\ x=-3\)
-7(3x - 5) + 2(7x - 14) = 28
-21x + 35 + 14x - 28 = 28
-7x = 28 - 35 + 28
-7x = 21
x = 21 : (-7)
x = -3