Tìm x
a) ( x2- 6x+ 9)2 - 15 (x2- 6x + 10) = 1
b) (x2- 9) = 12x + 1
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a)
\(x^3+\left(x-5\right)\left(x+8\right)=2x^2-37\\ \Leftrightarrow x^3+x^2+3x-40=2x^2-37\\ \Leftrightarrow x^3-x^2+3x-3=0\\ \Leftrightarrow x^2\left(x-3\right)+3\left(x-3\right)=0\\ \Leftrightarrow\left(x^2+3\right)\left(x-3\right)=0\)
Vì \(x^2+3\ge3>0\Rightarrow x-3=0\\ \Leftrightarrow x=3\)
b)
\(x\left(x-1\right)\left(x+1\right)\left(x+2\right)=24\\ \Leftrightarrow\left[x\left(x+1\right)\right]\left[\left(x-1\right)\left(x+2\right)\right]=24\\ \Leftrightarrow\left(x^2+x\right)\left(x^2+x-2\right)=24\)
Đặt \(x^2+x=y\)
\(\Rightarrow y\left(y-2\right)=24\\ \Leftrightarrow y^2-2y+1=25\\ \Leftrightarrow\left(y-1\right)^2=25\\ \Leftrightarrow\left[{}\begin{matrix}y-1=5\\y-1=-5\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}y=6\\y=-4\end{matrix}\right.\)
Nếu y = 6
\(\Rightarrow x^2+x=6\\ \Leftrightarrow x^2+x-6=0\\ \Leftrightarrow x^2+2x-3x-6=0\\ \Leftrightarrow x\left(x+2\right)-3\left(x+2\right)=0\\ \Leftrightarrow\left(x-3\right)\left(x+2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+2=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=3\\x=-2\end{matrix}\right.\)
Nếu y = -4
\(\Rightarrow x^2+x=-4\\ \Leftrightarrow x^2+x+\dfrac{1}{4}=-4+\dfrac{1}{4}\\ \Leftrightarrow\left(x+\dfrac{1}{2}\right)^2=-\dfrac{15}{4}\)
Mà \(\left(x+\dfrac{1}{.2}\right)^2\ge0>-\dfrac{15}{4}\)
`=> Loại`
c) Vế còn lại là bao nhiêu?
a:
ĐKXĐ: \(x^2+3x>=0\)
=>x(x+3)>=0
=>\(\left[{}\begin{matrix}x>=0\\x< =-3\end{matrix}\right.\)
\(\sqrt{16}-\sqrt{x^2+3x}=0\)
=>\(\sqrt{x^2+3x}=\sqrt{16}\)
=>x^2+3x=16
=>x^2+3x-16=0
\(\text{Δ}=3^2-4\cdot1\cdot\left(-16\right)=9+64=73>0\)
Do đó: Phương trình có 2 nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{-3-\sqrt{73}}{2}\\x_2=\dfrac{-3+\sqrt{73}}{2}\end{matrix}\right.\)
b:
ĐKXĐ: \(x\in R\)
\(3x-1-\sqrt{4x^2-12x+9}=0\)
=>\(\sqrt{\left(2x-3\right)^2}=3x-1\)
=>\(\left\{{}\begin{matrix}3x-1>=0\\\left(3x-1\right)^2=\left(2x-3\right)^2\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x>=\dfrac{1}{3}\\\left(3x-1-2x+3\right)\left(3x-1+2x-3\right)=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x>=\dfrac{1}{3}\\\left(x+2\right)\left(5x-4\right)=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\left(loại\right)\\x=\dfrac{4}{5}\left(nhận\right)\end{matrix}\right.\)
c:
ĐKXĐ: \(\left\{{}\begin{matrix}x^2-6x+8>=0\\2x^2-10x+11>=0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\left[{}\begin{matrix}x>=4\\x< =2\end{matrix}\right.\\\left[{}\begin{matrix}x< =\dfrac{5-\sqrt{3}}{2}\\x>=\dfrac{5+\sqrt{3}}{2}\end{matrix}\right.\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x< =\dfrac{5-\sqrt{3}}{2}\\x>=4\end{matrix}\right.\)
\(\sqrt{2x^2-10x+11}=\sqrt{x^2-6x+8}\)
\(\Leftrightarrow2x^2-10x+11=x^2-6x+8\)
=>\(x^2-4x+3=0\)
=>(x-1)(x-3)=0
=>x=3(loại) hoặc x=1(nhận)
a: ĐKXĐ: \(x^2-6x+6\ge0\)
=>\(x^2-6x+9-3\ge0\)
=>\(\left(x-3\right)^2-3\ge0\)
=>\(\left(x-3\right)^2\ge3\)
=>\(\left[\begin{array}{l}x-3\ge\sqrt3\\ x-3\le-\sqrt3\end{array}\right.\Rightarrow\left[\begin{array}{l}x\ge\sqrt3+3\\ x\le-\sqrt3+3\end{array}\right.\)
Ta có: \(x^2-6x+9=4\sqrt{x^2-6x+6}\)
=>\(x^2-6x+6-4\cdot\sqrt{x^2-6x+6}+3=0\)
=>\(\left(\sqrt{x^2-6x+6}-3\right)\left(\sqrt{x^2-6x+6}-1\right)=0\)
TH1: \(\sqrt{x^2-6x+6}-3=0\)
=>\(\sqrt{x^2-6x+6}=3\)
=>\(x^2-6x+6=9\)
=>\(x^2-6x-3=0\)
=>\(x^2-6x+9-12=0\)
=>\(\left(x-3\right)^2=12\)
=>\(\left[\begin{array}{l}x-3=2\sqrt3\\ x-3=-2\sqrt3\end{array}\right.\Rightarrow\left[\begin{array}{l}x=2\sqrt3+3\left(nhận\right)\\ x=3-2\sqrt3\left(nhận\right)\end{array}\right.\)
TH2: \(\sqrt{x^2-6x+6}-1=0\)
=>\(x^2-6x+6=1\)
=>\(x^2-6x+5=0\)
=>(x-1)(x-5)=0
=>\(\left[\begin{array}{l}x=1\left(nhận\right)\\ x=5\left(nhận\right)\end{array}\right.\)
b: ĐKXĐ: x∈R
\(x^2-x+8-4\sqrt{x^2-x+4}=0\)
=>\(x^2-x+4-4\cdot\sqrt{x^2-x+4}+4=0\)
=>\(\left(\sqrt{x^2-x+4}-2\right)^2=0\)
=>\(\sqrt{x^2-x+4}-2=0\)
=>\(\sqrt{x^2-x+4}=2\)
=>\(x^2-x+4=4\)
=>\(x^2-x=0\)
=>x(x-1)=0
=>x=0 hoặc x=1
c: \(x^2+\sqrt{4x^2-12x+44}=3x+4\)
=>\(x^2-3x-4+2\sqrt{x^2-3x+11}=0\)
=>\(x^2-3x+11+2\sqrt{x^2-3x+11}-15=0\)
=>\(\left(\sqrt{x^2-3x+11}+5\right)\left(\sqrt{x^2-3x+11}-3\right)=0\)
=>\(\sqrt{x^2-3x+11}-3=0\)
=>\(\sqrt{x^2-3x+11}=3\)
=>\(x^2-3x+11=9\)
=>\(x^2-3x+2=0\)
=>(x-1)(x-2)=0
=>x=1(nhận) hoặc x=2(nhận)
1)(x2-4x+16)(x+4)-x(x+1)(x+2)+3x2=0
\(\Rightarrow\)(x3+64)-x(x2+2x+x+2)+3x2=0
\(\Rightarrow\)x3+64-x3-2x2-x2-2x+3x2=0
\(\Rightarrow\)-2x+64=0
\(\Rightarrow\)-2x=-64
\(\Rightarrow\)x=\(\dfrac{-64}{-2}\)
\(\Rightarrow x=32\)
2)(8x+2)(1-3x)+(6x-1)(4x-10)=-50
\(\Rightarrow\)8x-24x2+2-6x+24x2-60x-4x+10=50
\(\Rightarrow\)-62x+12=50
\(\Rightarrow\)-62x=50-12
\(\Rightarrow\)-62x=38
\(\Rightarrow\)x=\(-\dfrac{38}{62}=-\dfrac{19}{31}\)
A, => (x-2)(x+2)(x-3)(x-3)=0
\(\Leftrightarrow\left[\begin{matrix}x-2=0\\x+2=0\\x-3=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=2\\x=-2\\x=3\\x=-3\end{matrix}\right.\)
Vậy tập no của pt ..
B, \(\Leftrightarrow x^2+2x+5x+10=0\)
\(\Leftrightarrow x\left(x+2\right)+5\left(x+2\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(x+5\right)=0\)
\(\Leftrightarrow\left[\begin{matrix}x+2=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=-2\\x=-5\end{matrix}\right.\)
Vậy ...............
C, \(\Leftrightarrow3x^2-6x-6x+12=0\)
\(\Leftrightarrow3x\left(x-2\right)-6\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(3x-6\right)=0\)
\(\Leftrightarrow\left[\begin{matrix}x-2=0\\3x-6=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=2\\x=2\end{matrix}\right.\)
Vậy tập no của pt là S{2}
\(a,\Leftrightarrow6x^2-6x^2-11x+10=-12\\ \Leftrightarrow-11x=-22\\ \Leftrightarrow x=2\\ b,\Leftrightarrow x^3+27-x^3-2x=12-5x\\ \Leftrightarrow3x=-15\\ \Leftrightarrow x=-5\\ c,\Leftrightarrow x^2-6x-16=0\\ \Leftrightarrow\left(x-8\right)\left(x+2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=8\\x=-2\end{matrix}\right.\)
a: ta có: \(6x^2-\left(2x+5\right)\left(3x-2\right)=-12\)
\(\Leftrightarrow6x^2-6x^2+4x-15x+10=-12\)
\(\Leftrightarrow-11x=-22\)
hay x=2
b: Ta có: \(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x^2+2\right)=12-5x\)
\(\Leftrightarrow x^3+27-x^3-2x+5x=12\)
\(\Leftrightarrow x=-5\)
a,a) ( x2- 6x+ 9)2 - 15 (x2- 6x + 10) = 1
Đặt (x2-6x+9)=a\(\left(a\ge0\right)\)Ta có:
a2-15(a+1)=1
<=> a2-15a-15-1=0
<=>a2-15a-16=0
<=>a2-16a+a-16=0
<=>a(a-16)+(a-16)=0
<=>(a-16)(a+1)=0\(\Rightarrow\orbr{\begin{cases}a-16=0\\a+1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}a=16\\a=-1\end{cases}}}\)
Vậy...