Tìm x
a) 3x - 10 = 2x + 13
b) x + 12 = -5 - x
c) x + 5 - 10 - x
d) 6x + 2 ^ 3 = 2x - 12
e) 12 - x = x + 1
f) 14 - 4x = 3x + 20
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a) \(3x-10=2x+13\Leftrightarrow x=13+10=23\)
b) \(x+12=-5-x\Leftrightarrow2x=-17\Leftrightarrow x=-\frac{17}{2}\)
c) \(x+5=10-x\Leftrightarrow2x=5\Leftrightarrow x=\frac{5}{2}\)
d) \(6x+23=2x-12\Leftrightarrow4x=-35\Leftrightarrow x=-\frac{35}{4}\)
e) \(12-x=x+1\Leftrightarrow2x=11\Leftrightarrow x=\frac{11}{2}\)
f) \(14+4x=3x+20\Leftrightarrow x=20-14=6\)
g) \(2\left(x-1\right)+3\left(x-2\right)=x-4\Leftrightarrow2x-2+3x-6=x-4\)
\(\Leftrightarrow5x-8=x-4\Leftrightarrow4x=4\Leftrightarrow x=1\)
h ) \(3\left(4-x\right)-2\left(x-1\right)=x+20\Leftrightarrow12-3x-2x+2=x+20\)
\(\Leftrightarrow14-5x=x+20\Leftrightarrow6x=-6\Leftrightarrow x=-1\)
i ) \(4\left(2x+7\right)-3\left(3x-2\right)=24\Leftrightarrow8x+28-9x+6=24\)
\(\Leftrightarrow34-x=24\Leftrightarrow x=34-24=10\)
k) \(3\left(x-2\right)+2x=10\Leftrightarrow3x-6+2x=5x-6=10\)
\(\Leftrightarrow5x=10+6=16\Leftrightarrow x=\frac{16}{5}\)
Tự KL cho các phần
a) \(3x-10=2x+13\)
\(\Leftrightarrow3x-2x=13+10\)
\(\Leftrightarrow x=23\)
b) \(x+12=-5-x\)
\(\Leftrightarrow x+x=-5-12\)
\(\Leftrightarrow2x=-17\)
\(\Leftrightarrow x=-\frac{17}{2}\)
c) \(x+5=10-x\)
\(\Leftrightarrow x+x=10-5\)
\(\Leftrightarrow2x=5\)
\(\Leftrightarrow x=\frac{5}{2}\)
d) \(6x+2^3=2x-12\)
\(\Leftrightarrow6x+8=2x-12\)
\(\Leftrightarrow6x-2x=-12-8\)
\(\Leftrightarrow4x=-20\)
\(\Leftrightarrow x=-5\)
e) \(12-x=x+1\)
\(\Leftrightarrow-x-x=1-12\)
\(\Leftrightarrow-2x=-11\)
\(\Leftrightarrow x=\frac{11}{2}\)
g) \(2\left(x-1\right)+3\left(x-2\right)=x-4\)
\(\Leftrightarrow2x-2+3x-6=x-4\)
\(\Leftrightarrow2x+3x-x=-4+6+2\)
\(\Leftrightarrow4x=4\)
\(\Leftrightarrow x=1\)
h) \(14+4x=3x+20\)
\(\Leftrightarrow4x-3x=20-14\)
\(\Leftrightarrow x=6\)
i) \(4\left(2x+7\right)-3\left(3x-2\right)=24\)
\(\Leftrightarrow8x+28-9x+6=24\)
\(\Leftrightarrow8x-9x=24-6-28\)
\(\Leftrightarrow-x=-10\)
\(\Leftrightarrow x=10\)
k) \(3\left(4-x\right)-2\left(x-1\right)=x+20\)
\(\Leftrightarrow12-3x-2x+2=x+20\)
\(\Leftrightarrow-3x-2x-x=20-2-12\)
\(\Leftrightarrow-6x=6\)
\(x=-1\)
l) \(3\left(x-2\right)+2x=10\)
\(\Leftrightarrow3x-6+2x=10\)
\(\Leftrightarrow3x+2x=10+6\)
\(\Leftrightarrow5x=16\)
\(\Leftrightarrow x=\frac{16}{5}\)
Lần sau bạn chỉ nên đăng ít câu hỏi một thôi nhé, đăng nnay các bạn làm không xuể đâu
x + 12 =(-5)-x
x + x = -5 - 12
2x = -17
\(x=-\frac{17}{2}\)
x + 5 = 10 - x
x + x = 10 - 5
2x = 5
\(x=\frac{5}{2}\)
12-x=x+1
12 - 1 = x+x
11=2x
x=\(\frac{11}{2}\)
14+4x=3x-20
4x-3x=-20-14
x=-34
a) x+3=12
x=12-3
x=9
b)(x-3):2=514:512
=>(x-3):2=52
=>(x-3):2=25
=>x-3=25.2
=>x-3=50
=>x=50+3
=>x=53
c)4x+3x=30-20:10
=>x(4+3)=30-2
=>7x=28
=>x=28:7
=>x=4
d)2x-138=23.32
=>2x-138=8.9
=>2x-138=72
=>2x=72+138
=>2x=210
=>x=210:2
=>x=105
a) x + 3 = 12
x = 12 - 3
x = 9
b) ( x - 3 ) : 2 = 514 : 512
( x - 3 ) : 2 = 514-12
( x - 3 ) : 2 = 52
( x - 3 ) : 2 = 25
x - 3 = 50
x = 53
c) 4x + 3x = 30 - 20 : 10
7x = 28
x = 4
d) 2x - 138 = 23 x 32
2x - 138 = 8 x 9
2x - 138 = 72
2x = 210
x = 105
a: \(\left(2x-3\right)\left(3x^2+1\right)-6x\left(x^2-x+1\right)+3x^2-2x=10\)
\(\Leftrightarrow6x^3+2x-9x^2-3-6x^3+6x^2-6x+3x^2-2x=10\)
\(\Leftrightarrow-6x-3=10\)
=>-6x=13
hay x=-13/6
b: \(\Leftrightarrow3x^2-3x+x-2-3x^2+5x=-8-5x\)
=>3x-2=-5x-8
=>8x=-6
hay x=-3/4
c: \(\Leftrightarrow64x^3-27-64x^3+32x^2-32x^2+x=20\)
=>x-27=20
hay x=47
a) \(\Rightarrow72-20x-36x+84=30x-240-6x-84\)
\(\Rightarrow80x=480\Rightarrow x=6\)
b) \(\Rightarrow15x+25-8x+12=5x+6x+36+1\)
\(\Rightarrow4x=0\Rightarrow x=0\)
c) \(\Rightarrow10x-16-12x+15=12x-16+11\)
\(\Rightarrow14x=4\Rightarrow x=\dfrac{2}{7}\)
Đề hơi khó hiểu nhưng vẫn biết cách làm !!!
Bài giải
a) +)Ta có : 4x - 7 = 12x +5
=> 4x - 12x = 5 + 7
<=> -8x = 12
<=> x =\(\frac{-12}{8}=\frac{-3}{2}\)
+)Ta có : 2x -1 = 6x + 5
<=> 2x - 6x = 5 + 1
<=> -4x = 6
<=> x = \(\frac{-6}{4}=\frac{-3}{2}\)
=> đây là cặp phương trình tương đương .
b) +) 7.( x - 10 ) =12
+) 14 . ( x - 10 ) = 24
<=> \(\frac{1}{2}.\left[14.\left(x-10\right)\right]=\frac{1}{2}.24\)
<=>7 . ( x - 10 ) = 12
=> Đây là 2 phương trình tương đương .
c) +) \(\frac{4}{x+3}-3=\frac{4}{x+3}+x.\left(ĐK:x\ne-3\right)\)
<=> \(\left(\frac{4}{x+3}-\frac{4}{x+3}\right)-3=x\)
<=> 0 - 3 = x
<=>x = 3
+) Với x= -3 => x + 3 = 0
=> ko thỏa mãn
=> ko xét tính tương đương
a) 3x - 10 = 2x + 13
<=> 3x - 2x = 13+10
<=> x = 23
Vậy x = 23
b) x + 12 = -5 - x
<=> x + x = -5 - 12
<=> 2x = -17
<=> x = -17 : 2
<=> x = -8,5
Vậy x = -8,5
c) x + 5 = 10 - x
<=> x + x = 10 - 5
<=> 2x = 5
<=> x = 5 : 2
<=> x = 2,5
Vậy x = 2,5
d) 6x + 2 ^ 3 = 2x - 12
<=> 6x + 8 = 2x - 12
<=> 6x - 2x = -12 - 8
<=> 4x = -20
<=> x = -20 : 4
<=> x = -5
Vậy x = -5
e) 12 - x = x + 1
<=> -x - x = 1 - 12
<=> -2x = -11
<=> x = -11 : (-2)
<=> x = 5,5
Vậy x= 5,5
f) 14 - 4x = 3x + 20
<=> -4x - 3x = 20 - 14
<=> -7x = 6
<=> x = 6 : (-7)
<=> x = \(-\frac{6}{7}\)