tim x biet :
a) ( 2x^2+4 ) - (x^2-3/2 ) = (-3+4x^2)+ ( -4x^2/3+1)
b) ( I xI -4) - ( 2- I-xI ) = 1/3 . I xI -5
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a: \(\Leftrightarrow2x^2+4-x^2+\dfrac{3}{2}=-3+4x^2-\dfrac{4}{3}x^2+1\)
\(\Leftrightarrow x^2+\dfrac{11}{2}=\dfrac{8}{3}x^2-2\)
\(\Leftrightarrow x^2\cdot\dfrac{-5}{3}=-\dfrac{15}{2}\)
\(\Leftrightarrow x^2=\dfrac{9}{2}\)
hay \(x\in\left\{\dfrac{3\sqrt{2}}{2};-\dfrac{3\sqrt{2}}{2}\right\}\)
b: \(\Leftrightarrow\left|x\right|-4-2+\left|x\right|-\dfrac{1}{3}\left|x\right|+5=0\)
\(\Leftrightarrow\left|x\right|\cdot\dfrac{5}{3}=1\)
hay \(x\in\left\{\dfrac{3}{5};-\dfrac{3}{5}\right\}\)
\(2x^2+4-\left(x^2-\frac{3}{2}\right)=\left(-3+4x^2\right)+\left(-\frac{4x^2}{3}+1\right)\)
\(2x^2-x^2+4+\frac{3}{2}=\)\(-3+1+4x^2-\frac{4x^2}{3}\)
\(x^2+\frac{11}{2}=-2+-\frac{16x^2}{3}\)
\(x^2+\frac{16x^2}{3}=\frac{-11}{2}-2=-\frac{15}{2}\)
\(\frac{19x^2}{3}=-\frac{15}{2}\)
\(19x^2=\frac{-15}{2}.3=-\frac{45}{2}\)
\(x^2=\frac{-45}{2}:19=-\frac{45}{38}\)
<=>/x/-4-2+/-x/=1/3/x/-5
<=>/x/-6+/-x/=1,3/x/-5
<=>-0,3/x/+/-x/=1
Th1 với x<0
=>/x/=-x ; /-x/=x
khi đó ta có:
-0,3.(-x) + x=1
<=>0,3x + x=1
<=>1,3x=1
<=>x=10/13
TH2 \(x\ge0\)
/x/=x;/-x/=-x
Khi đó ta có
-0,3x-x=1
<=>-1,3x=1
<=>x=-10/13
k nha
Bài 1:
a) \(4x\left(3x-1\right)-2\left(3x+1\right)-\left(x+3\right)\)
\(=12x^2-4x-6x-2-x-3\)
\(=12x^2-11x-5\)
b) \(=\left(-2x^2-1xy+2y^2\right)\left(-1x^2y\right)\)
\(=\left[\left(-1x^2y\right)\left(-2x^2\right)\right]-\left[\left(-1x^2y\right).1xy\right]+\left[\left(-1x^2y\right).2y^2\right]\)
\(=\left(2x^4y\right)-\left(-1x^3y^2\right)+\left(-2x^2y^3\right)\)
\(=2x^4y+1x^3y^2-2x^2y^3\)
c) \(4x\left(3x^2-x\right)-\left(2x+3\right)^2\left(6x^2-3x+1\right)\)
\(=\left(4x.3x^2\right)-\left(4x.x\right)-\left[\left(2x\right)^2+2.2x.3+3^2\right]\left(6x^2-3x+1\right)\)
\(=12x^3-4x^2-\left(4x^2+12x+9\right)\left(6x^2-3x+1\right)\)
\(=12x^3-4x^2-\left[4x^2\left(6x^2-3x+1\right)+12x\left(6x^2-3x+1\right)+9\left(6x^2-3x+1\right)\right]\)
\(=12x^3-4x^2-\left[\left(24x^4-12x^3+4x^2\right)+\left(72x^3-36x^2+12x\right)+\left(36x^2-27x+9\right)\right]\)
\(=12x^3-4x^2-24x^4+12x^3-4x^2-72x^3+36x^2-12x-36x^2+27x-9\)
\(=-48x^3-8x^2-24x^4+15x-9\)