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6 tháng 8 2018
\(a,\left(3x+x\right)\left(x^2-9\right)-\left(x-3\right)\left(x^2+3x+9\right)\)
\(=4x\left(x^2-9\right)-x^3+27\)
\(=4x^3-36x-x^3+27\)
\(=3x^3-36x+27\)
6 tháng 8 2018
\(\left(x+6\right)^2-2x.\left(x+6\right)+\left(x-6\right).\left(x+6\right)\)
\(=\left(x+6\right).\left(x+6-2x+x-6\right)\)
\(=\left(x+6\right).0\)
\(=0\)
LT
1
24 tháng 6 2017
a)\(2x\left(x+1\right)-3-2x=5\)
\(\Leftrightarrow2x^2+2x-3-2x=5\)
\(\Leftrightarrow2x^2=8\)
\(\Leftrightarrow x^2=4=\left(-2\right)^2=2^2\)
\(\Rightarrow x=2;-2\)
b)\(2x\left(3x+1\right)+\left(4-2x\right)=7\)
\(\Leftrightarrow6x^2+2x+4-2x=7\)
\(\Leftrightarrow6x^2+4=7\)
\(\Leftrightarrow6x^2=3\)
\(\Leftrightarrow x^2=\frac{1}{2}=-\sqrt{\frac{1}{2}}=\sqrt{\frac{1}{2}}\)
c)\(\left(x-3\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x-1\right)^2=6\)
\(\Leftrightarrow x^3-9x^2+27x-27-x^3+27+6\left(x^2-2x+1\right)=6\)
\(\Leftrightarrow-3x^2+27x+6x^2-12x+6=6\)
\(\Leftrightarrow-3x^2+27x+6x^2-12x+6=6\)
\(\Leftrightarrow3x^2+15x=0\)
\(\Leftrightarrow3x\left(x+5\right)=0\)
\(\Rightarrow\orbr{\begin{cases}3x=0\\x+5=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=0\\x=-5\end{cases}}\)
LT
0
D
2
5 tháng 7 2018
\(a,\left(x+3\right)\left(x-3\right)-\left(x-2\right)\left(x+5\right)=6\)
\(\Leftrightarrow x^2-9-x^2-5x+2x+10=6\)
\(\Leftrightarrow-3x+1=6\Leftrightarrow x=\frac{-5}{3}\)
Vậy x =\(\frac{-5}{3}\)
\(b,\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x+1\right)-\left(x-6\right)\)
\(\Leftrightarrow6x^2+27x+4x+18-6x^2-x-12x-2=x+1-x+6\)
\(\Leftrightarrow18x+16=7\Leftrightarrow x=\frac{-1}{2}\)
Vậy x =\(\frac{-1}{2}\)
HH
5 tháng 7 2018
a/ \(\left(x+3\right)\left(x-3\right)-\left(x-2\right)\left(x+5\right)=6\)
<=> \(x^2-9-\left(x^2+3x-10\right)=6\)
<=> \(x^2-9-x^2-3x+10=6\)
<=> \(-3x+1=6\)
<=> \(-3x=5\)
<=> \(x=-\frac{5}{3}\)
b/ \(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x+1\right)-\left(x-6\right)\)
<=> \(6x^2+31x+18-\left(6x^2+13x+2\right)=x+1-x+6\)
<=> \(6x^2+31x+18-6x^2-13x-2=7\)
<=> \(18x+16=7\)
<=> \(18x=-9\)
<=> \(x=-\frac{1}{2}\)
16 tháng 6 2016
(3x+2)(2x+9)-(x+2)(6x+1)=(x+1)-(x-6)
6x^2+27x+4x+18-6x^2-x-12x-2=x+1-x+6
18x+16=7
18x=7-16
x=-9/18=-2
vậy x =-2
LM
21 tháng 8 2016
a) (x + 2) . (x + 3) - (x - 2) . (x + 5) = 6
=> (x . x + 3x + 2x + 2 . 3) - (x . x + 5x - 2x - 2 . 5) = 6
=> (x2 + 5x + 6) - (x2 + 3x - 10) = 6
=> x2 + 5x + 6 - x2 - 3x + 10 = 6
=> 2x +16 = 6 => 2x = -10 => x = -5
b) (3x + 2) . (2x + 9) - (x + 2) . (6x + 1) = (x + 1) - (x - 6)
=> (3x . 2x + 3x . 9 + 2 . 2x + 2 . 9) - (x . 6x + 1x + 2 . 6x + 2 .1) = x + 1 - x + 6
=> (6x2 + 31x + 18) - (6x2 + 13x + 2) = 7
=> 6x2 + 31x + 18 - 6x2 - 13x - 2 = 7
=> 18x + 16 = 7 => 18x = 9 => x = 0,5
c) 3 . (2x - 1) . (3x - 1) - (2x - 3) . (9x - 1) = 0
=> 3(2x . 3x - 2x -3x + 1) - (2x . 9x - 2x -3 . 9x + 3) = 0
=> 3(6x2 - 5x +1) - (18x2 - 29x + 3) = 0
=> (18x2 -15x + 1) -(18x2 - 29x +3) = 0
=> 18x2 - 15x +1 -18x2 + 29x - 3 = 0
=> 14x = 0 => x = 0
\(\left(x-1\right)\left(x+1\right)-3x-6=6\)
\(x^2-1^2-3x-6-6=0\)
\(x^2-1-3x-12=0\)
\(x^2-3x-13=0\)
\(\orbr{\begin{cases}x=\frac{3-\sqrt{61}}{2}\\x=\frac{3+\sqrt{61}}{2}\end{cases}}\)
\(\left(x-1\right)\left(x+1\right)-3x-6=6\)
\(\left(x-1\right)\left(x+1\right)-3x=12\)
\(\left(x-1\right)x-\left(x-1\right)1-\left(1+2\right)x=12\)
\(\left(x-1-1+2\right)x-x-1=12\)
\(\left(x-1-1+2-1\right)x=11\)
\(\left(x-1\right)x=11\)
\(x^2-x=11\)
Đk : x > 4
\(x=4\Rightarrow16-4=11\left(\varnothing\right)\)
\(x\in\varnothing\)