(10x+9)x-(5x-1)(2x+3)=8 Tìm x
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TT
1
10 tháng 7 2015
\(\left(10+9\right)x-\left(5x-1\right)\left(2x+3\right)=8\)
\(\Rightarrow19x-\left(10x^2+15x-2x-3\right)=8\)
\(\Rightarrow19x-10x^2-15x+2x+3=8\)
\(\Rightarrow\left(19x-15x+2x\right)-10x^2+3=8\)
\(\Rightarrow6x-10x^2+3=8\)
\(\Rightarrow6x-10x^2=5\)
mk nghĩ à đề có nhầm lẫn
TT
1
MT
11 tháng 7 2015
(10x+9)x-(5x-1)(2x+3)=8
<=>10x2+9x-(10x2+15x-2x-3)=8
<=>10x2+9x-10x2-15x+2x+3=8
<=>-4x+3=8
<=>-4x=5
<=>x=-5/4
26 tháng 10 2021
\(e,\Leftrightarrow x^2-10x+21-x^2=1\\ \Leftrightarrow-10x=-20\Leftrightarrow x=2\\ f,\Leftrightarrow x^2+4x+4-x^2+3x-2=0\\ \Leftrightarrow7x=-2\Leftrightarrow x=-\dfrac{2}{7}\\ g,=x^2-2x+1-x^2+4=-2x+5\\ h,\Leftrightarrow10x^2+9x-10x^2-13x+3=8\\ \Leftrightarrow-4x=5\Leftrightarrow x=-\dfrac{5}{4}\)
26 tháng 10 2021
e) \(\left(x-3\right)\left(x-7\right)-x^2=1\\ \Rightarrow x^2-10x+21-x^2=1\\ \Rightarrow-10x=-20\\ \Rightarrow x=2\)
f) \(\left(x+2\right)^2-\left(x-2\right)\left(x-1\right)=0\\ \Rightarrow x^2+4x+4-x^2+3x-2=0\\ \Rightarrow7x=-2\\ \Rightarrow x=-\dfrac{2}{7}\)
g) \(\left(x-1\right)^2-\left(x-2\right)\left(x+2\right)=0\\ \Rightarrow x^2-2x+1-x^2+4=0\\ \Rightarrow-2x=-5\\ \Rightarrow x=\dfrac{5}{2}\)
h) \(\left(10x+9\right).x-\left(5x-1\right)\left(2x+3\right)=8\\ \Rightarrow10x^2+9x-10x^2-13x+3=8\\ \Rightarrow-4x=5\\ \Rightarrow x=-\dfrac{5}{4}\)
23 tháng 1 2022
5: \(\Leftrightarrow9\left(x^2-5x-4\right)=36\left(x+1\right)+8\left(x^2-10x\right)\)
\(\Leftrightarrow9x^2-45x-36-36x-36-8x^2+80x=0\)
\(\Leftrightarrow x^2-x-72=0\)
=>(x-9)(x+8)=0
=>x=9 hoặc x=-8
6: \(\Leftrightarrow x^2-9=9x-x^2-9+x\)
\(\Leftrightarrow2x^2-10x=0\)
=>2x(x-5)=0
=>x=0 hoặc x=5
23 tháng 1 2022
5, <=> 9x^2 - 45x - 36 = 36x + 36 + 8x^2 - 80x
<=> x^2 - x - 72 = 0 <=> x = 9 ; x = -8
6, <=> x^2 - 9 = 9x - x^2 - 9 + x = 10x - x^2 - 9
<=> 2x^2 - 10x = 0 <=> x = 0 ; x = 5
7, <=> (x-1)^2 = (3x+3)^2
<=> (x-1-3x-3)(x-1+3x+3) = 0
<=> (-2x-4)(4x+2) = 0 <=> x = -2;x=-1/2
8, = (x^2-10x-15)(x^2-10x+25)
25 tháng 8 2020
a) ( 3x + 2 )( x - 1 ) - ( x + 2 )( 3x + 1 ) = 7
<=> 3x2 - x - 2 - ( 3x2 + 7x + 2 ) = 7
<=> 3x2 - x - 2 - 3x2 - 7x - 2 = 7
<=> -8x - 4 = 7
<=> -8x = 11
<=> x = -11/8
b) ( 6x + 5 )( 2x + 3 ) - ( 4x + 3 )( 3x - 2 ) = 8
<=> 12x2 + 28x + 15 - ( 12x2 + x - 6 ) = 8
<=> 12x2 + 28x + 15 - 12x2 - x + 6 = 8
<=> 27x + 21 = 8
<=> 27x = -13
<=> x = -13/27
c) 2x( x + 3 ) - ( x + 1 )( 2x + 1 ) - 5 = 9
<=> 2x2 + 6x - ( 2x2 + 3x + 1 ) - 5 = 9
<=> 2x2 + 6x - 2x2 - 3x - 1 - 5 = 9
<=> 3x - 6 = 9
<=> 3x = 15
<=> x = 5
d) ( 5x + 3 )( 4x - 7 ) - ( 10x + 9 )( 2x - 3 ) = 10
<=> 20x2 - 23x - 21 - ( 20x2 - 12x - 27 ) = 10
<=> 20x2 - 23x - 21 - 20x2 + 12x + 27 = 10
<=> -11x + 6 = 10
<=> -11x = 4
<=> x = -4/11
A
25 tháng 8 2020
a, \(\left(3x+2\right)\left(x-1\right)-\left(x+2\right)\left(3x+1\right)=7\Leftrightarrow-8x-4=7\Leftrightarrow x=-\frac{11}{8}\)
b, \(\left(6x+5\right)\left(2x+3\right)-\left(4x+3\right)\left(3x-2\right)=8\Leftrightarrow27x+21=8\Leftrightarrow x=-\frac{13}{27}\)
c, \(2x\left(x+3\right)-\left(x+1\right)\left(2x+1\right)-5=9\Leftrightarrow3x-6=9\Leftrightarrow x=5\)
d, \(\left(5x+3\right)\left(4x-7\right)-\left(10x+9\right)\left(2x-3\right)=10\Leftrightarrow-11x+6=10\Leftrightarrow x=-\frac{4}{11}\)
NN
Nguyễn Nhung
VIP
3 tháng 8 2020
(3x-1)(2x+7)+(x+1)(6x-5)=(x+2)-(x-5) x (10x+9)-(5x-1)(2x+3)=8
6x^2+21x-2x-7+6x^2-5x+6x-5=x+2-x+5 10x^2+9x-(10x^2+15x-2x-3)=8
12x^2+20x-12=7 10x^2+9x-10x^2-15x+2x+3=8
12x^2+20x=19 -4x=5
x(12x+20)=19 x=-5/4
x=19 hoac x=-1/12
9 tháng 7 2018
a)4(x+2)-7(2x-1)+9(3x-4)=30 b)2(5x-8)-3(4x-5)=4(3x-4)+11
<=>4x+8-14x+7+27x-36=30 <=>10x-16-12x+15=12x-16+11
<=>17x-21=30 <=> -14x=-4 <=>x=2/7
<=>17x=51
<=>x=3
16 tháng 6 2023
`@` `\text {Ans}`
`\downarrow`
`a)`
`3x(4x-1) - 2x(6x-3) = 30`
`=> 12x^2 - 3x - 12x^2 + 6x = 30`
`=> 3x = 30`
`=> x = 30 \div 3`
`=> x=10`
Vậy, `x=10`
`b)`
`2x(3-2x) + 2x(2x-1) = 15`
`=> 6x- 4x^2 + 4x^2 - 2x = 15`
`=> 4x = 15`
`=> x = 15/4`
Vậy, `x=15/4`
`c)`
`(5x-2)(4x-1) + (10x+3)(2x-1) = 1`
`=> 5x(4x-1) - 2(4x-1) + 10x(2x-1) + 3(2x-1)=1`
`=> 20x^2-5x - 8x + 2 + 20x^2 - 10x +6x - 3 =1`
`=> 40x^2 -17x - 1 = 1`
`d)`
`(x+2)(x+2)-(x-3)(x+1)=9`
`=> x^2 + 2x + 2x + 4 - x^2 - x + 3x + 3=9`
`=> 6x + 7 =9`
`=> 6x = 2`
`=> x=2/6 =1/3`
Vậy, `x=1/3`
`e)`
`(4x+1)(6x-3) = 7 + (3x-2)(8x+9)`
`=> 24x^2 - 12x + 6x - 3 = 7 + (3x-2)(8x+9)`
`=> 24x^2 - 12x + 6x - 3 = 7 + 24x^2 +11x - 18`
`=> 24x^2 - 6x - 3 = 24x^2 + 18x -11`
`=> 24x^2 - 6x - 3 - 24x^2 + 18x + 11 = 0`
`=> 12x +8 = 0`
`=> 12x = -8`
`=> x= -8/12 = -2/3`
Vậy, `x=-2/3`
`g)`
`(10x+2)(4x- 1)- (8x -3)(5x+2) =14`
`=> 40x^2 - 10x + 8x - 2 - 40x^2 - 16x + 15x + 6 = 14`
`=> -3x + 4 =14`
`=> -3x = 10`
`=> x= - 10/3`
Vậy, `x=-10/3`
(10x+9)x−(5x−1(2x+3)=810x2+9x−(10x2+15x−2x−3)=810x2+9x−(10x2+13x−3)=810x2+9x-10x2−13x+3=8−4x+3=8−4x=8−3−4x=5x=−45
Ta có: \(x\left(10x+9\right)-\left(5x-1\right)\left(2x+3\right)=8\)
=>\(10x^2+9x-\left(10x^2+15x-2x-3\right)=8\)
=>\(10x^2+9x-10x^2-13x+3=8\)
=>-4x=8-3=5
=>\(x=-\dfrac{5}{4}\)