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e) Ta có: \(E=\left(3x+2\right)\left(3x-5\right)\left(x-1\right)\left(9x+10\right)+24x^2\)
\(=\left(9x^2-15x+6x-10\right)\left(9x^2+10x-9x-10\right)+24x^2\)
\(=\left(9x^2-10-9x\right)\left(9x^2-10+x\right)+24x^2\)
\(=\left(9x^2-10\right)^2-8x\left(9x^2-10\right)-9x^2+24x^2\)
\(=\left(9x^2-10\right)^2-8x\left(9x^2-10\right)+15x^2\)
\(=\left(9x^2-10\right)^2-3x\left(9x^2-10\right)-5x\left(9x^2-10\right)+15x^2\)
\(=\left(9x^2-10\right)\left(9x^2-3x-10\right)-5x\left(9x^2-10-3x\right)\)
\(=\left(9x^2-3x-10\right)\left(9x^2-5x-10\right)\)
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Bạn tự phân tích đa thức thành nhân tử nhé!
\(1.\)
\(2x^3+x+3=0\)
\(\Leftrightarrow\) \(\left(x+1\right)\left(2x^2-2x+3\right)=0\) \(\left(1\right)\)
Vì \(2x^2-2x+3=2\left(x^2-x+1\right)+1=2\left(x-\frac{1}{2}\right)^2+\frac{1}{2}>0\) với mọi \(x\in R\)
nên từ \(\left(1\right)\) \(\Rightarrow\) \(x+1=0\) \(\Leftrightarrow\) \(x=-1\)
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Đặt x2-3x+4=a
=>\(\frac{1}{a-1}+\frac{2}{a}=\frac{6}{a+1}\)
ĐKXĐ:a khác 1 ; -1 ;0
=>a2+a+2a2-2=6a2-6a
<=>6a2-3a2-a-6a+2=0
<=>3a2-7a+2=0
<=>(3a-1)(a-2)=0
<=>a=1/3 hoặc a=2
*)a=1/3
=>x2-3x+4=1/3
<=>x2-3x+11/3=0
<=>(x-1,5)2+17/12=0(vô lí)
*)a=2
=>x2-3x+4=2
<=>x2-3x+2=0
<=>(x-1)(x-2)=0
<=>x=1 hoặc x=2
Vậy x={1;2}
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2x+3/x+1 - 6/x=2
<=>x(2x+3)/x(x+1) - 6(x+1)/x(x+1)=2x(x+1)/x(x+1)
<=>x(2x+3) - 6(x+1)=2x(x+1)
<=>2x^2+3x - 6x -6=2x^2 + 2x
<=>(2x^2 - 2x^2) + (3x - 6x - 2x)=6
<=>-5x =6
<=> x =-6/5
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\(\left(x-3\right)\left(x-5\right)\left(x-6\right)\left(x-10\right)=24x^2\)
<=>\(\left(x^2-13x+30\right)\left(x^2-11x+30\right)=24x^2\)
Đặt x2-11x+30=t => (t-2x).t=24x2 <=> t2-2xt=24x2 <=> t2-2xt-24x2=0 <=> 4xt-24x2+t2-6xt=0
<=>4x(t-6x)+t(t-6x)=0<=>(t-6x)(4x+t)=0<=>t-6x=0 hoặc 4x+t=0 <=>x2-17x+30=0 hoặc x2-7x+30=0
+)x2-17x+30=0 <=> x2-15x-2x+30=0 <=> x(x-15)-2(x-15)=0 <=> (x-2)(x-5)=0
<=>x-2=0 hoặc x-15=0 <=>x=2 hoặc x=15
+)x2-7x+30=0 <=> \(x^2-2.\frac{7}{2}.x+\frac{49}{4}+\frac{71}{4}=0\Leftrightarrow\left(x-\frac{7}{2}\right)^2+\frac{71}{4}=0\)
Vì \(\left(x-\frac{7}{2}\right)^2\ge0\Rightarrow\left(x-\frac{7}{2}\right)^2+\frac{71}{4}\ge\frac{71}{4}>0\) => vô nghiệm
Vậy x=2 hoặc x=15