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Bài 1:
a: Ta có: \(A=\left(k-4\right)\left(k^2+4k+16\right)-\left(k^3+128\right)\)
\(=k^3-64-k^3-128\)
=-192
b: Ta có: \(B=\left(2m+3n\right)\left(4m^2-6mn+9n^2\right)-\left(3m-2n\right)\left(9m^2+6mn+4n^2\right)\)
\(=8m^3+27n^3-27m^3+8n^3\)
\(=-19m^3+35n^3\)
Bài 4:
a: Ta có: \(\left(x-1\right)^3+\left(2-x\right)\left(4+2x+x^2\right)+3x\left(x+2\right)=16\)
\(\Leftrightarrow x^3-3x^2+3x-1+8-x^3+3x^2+6x=16\)
\(\Leftrightarrow9x=9\)
hay x=1
b: ta có: \(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2-2\right)=15\)
\(\Leftrightarrow x^3+8-x^3+2x=15\)
\(\Leftrightarrow2x=7\)
hay \(x=\dfrac{7}{2}\)
\(1\)) \(5-\left(10-x\right)=7\)
\(10-x=5-7\)
\(10-x=-2\)
\(x=10-\left(-2\right)\)
\(x=12\)
\(2\)) \(-32-\left(x-5\right)=0\)
\(x-5=-32-0\)
\(x-5=-32\)
\(x=-32+5\)
\(x=-27\)
2.
a. 3x(12x - 4) - 9x(4x - 3) = 30
<=> 36x2 - 12x - 36x2 + 27x = 30
<=> 36x2 - 36x2 - 12x + 27x = 30
<=> 15x = 30
<=> x = 2
b. x(5 - 2x) + 2x(x - 1) = 15
<=> 5x - 2x2 + 2x2 - 2x = 15
<=> -2x2 + 2x2 + 5x - 2x = 15
<=> 3x = 15
<=> x = 5
a) x2 ( 5x3 - x - 1212)= 5x5-x3-1212x
b) ( 3xy - x2 + y ) 2323x2y= 6969x3y2- 2323x4y+ 2323x2y2
c) x2 ( 4x3 - 5xy + 2x ) ( -1212 xy )=(4x5-5x3y+2x3).(-1212xy)
= -4848x6y +6060x4y2-2424x4y
2/ Tìm x, biết
a) 3x( 12x - 4 ) - 9x (4x - 3 ) = 30
=> 36x2-12x-36x2+27x=30
=> -12x +27x=30
=> 15x = 30
=>x =2
b ) x( 5 - 2x ) + 2x ( x - 1 )= 15
=> 5x-2x2+2x2-2x=15
=> 3x=15
=>x=5
b: =>4x^2+8x-8x^2+5x-10=0
=>-4x^2+13x-10=0
=>x=2 hoặc x=5/4
c: =>2x^2-5x+6x-15=2x^2+8x
=>x-15=8x
=>-7x=15
=>x=-15/7
d: =>3x^2+15x-2x-10-3x^2-12x=5
=>x-10=5
=>x=15
e: =>x^2-3x+2x^2+2x=3x^2-12
=>-x=-12
=>x=12
17x + 3. ( -16x – 37) = 2x + 43 - 4x
<=>17x-48x-111=-2x+43
<=>-29x=154
<=> \(x=-\frac{154}{29}\)
-3. (2x + 5) -16 < -4. (3 – 2x)
\(\Leftrightarrow-6x-31< -12+8x.\)
\(\Leftrightarrow-14x< 19\Rightarrow x< -\frac{19}{14}\)
nhớ giúp nhaaaaa
a) 2x - 15 = 13
=> 2x = 13 + 15
=> 2x = 28
=> x = 14
128 - (x + 5) = 23
=> x + 5 = 128 - 23
=> x + 5 = 105
=> x = 105 - 5
=> x = 100
[(x2 + 54) - 32] . 2 = 244
=> (x2 + 54) - 32 = 244 : 2
=> (x2 + 54) - 32 = 122
=> x2 + 54 = 122 + 32
=> x2 + 54 = 154
=> x2 = 154 - 54
=> x2 = 100
=> x2 = 102
=> x = 10
(3x - 1)3 = 125
=> (3x - 1)3 = 53
=> 3x - 1 = 5
=> 3x = 5 + 1
=> 3x = 6
=> x = 2
Bài 1: Tìm x biết
a, 2x - 15= 13
2x = 13 + 15
2x = 28
x = 28 : 2
x = 14
Vậy x = 14
128 - (x + 5)= 23
x + 5 = 128 - 23
x + 5 = 105
x = 105 - 5
x = 100
Vậy x = 100
[( x2+54) - 32].2= 244
( \(x^2\) + 54 ) - 32 = 244 : 2
( x2+54) - 32 = 122
x2+54 = 122 + 32
x2+54 = 154
x2 = 154 - 54
x2 = 100
\(x^2\) = \(10^2\)
x =10
(3x -1)3= 125
\(\left(3x-1\right)^3\) = \(5^3\)
3x -1 = 5
3x = 5 + 1
x = 6 : 3
x = 2
b, 100: ( 2x+5 )= 4
2x + 5 = 100 : 4
2x + 5 = 25
2x = 45 - 5
2x = 40
x = 40 : 2
x = 20
[( 8x-14 ) :2 - 2]. 31= 341
( 8x - 14 ) : 2 - 1 = 341 : 31
( 8x - 14 ) :2 -2 = 11
( 8x - 14 ) : 2 = 11 + 2
( 8x - 14 ) : 2 = 13
8x - 14 = 13 . 2
8x - 14 = 26
8x = 26 + 14
8x = 40
x = 40 : 8
x = 5
1230 :3 (x - 20 )= 10
3 ( x - 20 ) = 1230 : 10
3 ( x - 20 ) = 123
x - 20 = 123 : 3
x- 20 = 41
x = 41 + 20
x= 61
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