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a: 2x+16=30
=>2x=30-16=14
=>x=14/2=7
b: \(2\left(x+1\right)^3+5=59\)
=>\(2\left(x+1\right)^3=54\)
=>\(\left(x+1\right)^3=27\)
=>x+1=3
=>x=2
c: \(x\inƯ\left(24\right)\)
=>\(x\in\left\{1;2;3;4;6;8;12;24\right\}\)
mà 2<=x<=12
nên \(x\in\left\{2;3;4;6;8;12\right\}\)
d: \(x-2⋮5\)
=>\(x-2\in\left\{0;5;10;15;20;25;30;35;...\right\}\)
=>\(x\in\left\{2;7;12;17;22;27;32;...\right\}\)
mà x<=30
nên \(x\in\left\{2;7;12;17;22;27\right\}\)
a) 2.x + 16 = 30
2x = 30 - 16
2x = 14
x = 14 : 2
x = 7
b) 2.(x + 1)³ + 5 = 59
2.(x + 1)³ = 59 - 5
2.(x + 1)³ = 54
(x + 1)³ = 54 : 2
(x + 1)³ = 27
(x + 1)³ = 3³
x + 1 = 3
x = 3 - 1
x = 2
c) x ∈ Ư(20) = {1; 2; 4; 5; 10; 20}
Mà 2 ≤ x ≤ 12
⇒ x ∈ {2; 4; 5; 10}
d) (x - 2) ⋮ 5 nên x - 2 ∈ B(5) = {0; 5; 10; 15; 20; 25; 30; 35; ...}
x {2; 7; 12; 17; 22; 27; 32; 37; ...}
Mà x ≤ 30
⇒ x ∈ {2; 7; 12; 17; 22; 27}
a. 4(2x+7)-3(3x-2)=24
=> 8x+28-9x+6=24
=> -x+34=24
=> -x=-10=> x=10
b. 2(x-1)+3(x-2)=x-4
=> 2x-2+3x-6=x-4
=> 5x-8=x-4
=> 5x-x=-4+8
=> 4x=4=> x=1
c. [124-(20-4x)]:30+7=11
=> (124-20+4x):30=4
=> (104+4x):30=4
=> 104+4x=120
=> 4x=96 => x=24
2x-1 | -1 | 3 | -3 | 1 | 2 | ||
y+5 | -30 | 10 | -10 | 30 | |||
x | |||||||
y |
Bạn tự điền , chú ý 2x-1 là số lẻ
a) 0,5 x - \(\frac{2}{3}\)x = \(\frac{7}{12}\)
x . ( 0,5 - \(\frac{2}{3}\)) = \(\frac{7}{12}\)
x . \(\frac{-1}{6}\) = \(\frac{7}{12}\)
x = \(\frac{7}{12}\): \(\frac{-1}{6}\)
x = \(\frac{-7}{2}\)
b) x : \(\frac{25}{3}\) = -25
x = -25 . \(\frac{25}{3}\)
x = \(\frac{-625}{3}\)
c) 5,5 x = \(\frac{13}{15}\)
x = \(\frac{13}{15}\): 5,5
x = \(\frac{26}{165}\)
d) (\(\frac{3x}{7}\)+ 1 ) : ( -4) = \(\frac{-1}{28}\)
( \(\frac{3x}{7}\)+ 1 ) = \(\frac{-1}{28}\). ( -4)
\(\frac{3x}{7}\)+ 1 = \(\frac{1}{7}\)
\(\frac{3x}{7}\) = \(\frac{1}{7}\)- 1
\(\frac{3x}{7}\) = \(\frac{-6}{7}\)
=> x = -2
e) y + 30% y = -1,3
y + \(\frac{3}{10}\)y = -1,3
y . ( 1 + \(\frac{3}{10}\)) = -1,3
y . \(\frac{13}{10}\) = -1,3
y = -1,3 : \(\frac{13}{10}\)
y = -1
g) y - 25% y = \(\frac{1}{2}\)
y - \(\frac{1}{4}\)y = \(\frac{1}{2}\)
y . ( 1 - \(\frac{1}{4}\)) = \(\frac{1}{2}\)
y . \(\frac{3}{4}\) = \(\frac{1}{2}\)
y = \(\frac{1}{2}\): \(\frac{3}{4}\)
y = \(\frac{2}{3}\)
ai tốt bụng thì tk cho mk nha, mk đg âm điểm đây huhu
1: Ta có: \(20-2\left(x+4\right)=4\)
\(\Leftrightarrow2\left(x+4\right)=16\)
\(\Leftrightarrow x+4=8\)
hay x=4
5: Ta có: \(\left(x+1\right)^3=27\)
\(\Leftrightarrow x+1=3\)
hay x=2
Bài 3:
a: Ta có: \(3x^2=75\)
\(\Leftrightarrow x^2=25\)
hay \(x\in\left\{5;-5\right\}\)
b: Ta có: \(2x^3=54\)
\(\Leftrightarrow x^3=27\)
hay x=3
Bài 2:
b: Ta có: \(30-3\cdot2^n=24\)
\(\Leftrightarrow3\cdot2^n=6\)
\(\Leftrightarrow2^n=2\)
hay n=1
c: Ta có: \(40-5\cdot2^n=20\)
\(\Leftrightarrow5\cdot2^n=20\)
\(\Leftrightarrow2^n=4\)
hay n=2
d: Ta có: \(3\cdot2^n+2^n=16\)
\(\Leftrightarrow2^n\cdot4=16\)
\(\Leftrightarrow2^n=4\)
hay n=2