Phân tích đa thức thành nhân tử
bằng phương pháp nhóm hạng tử:
a,2x3+3x2+2x+3
b,a2-ab+a-b
c,2x2+4x+2-2y2
d,x4-2x3+10x2-20x=0
e,x3 +2x2+x
f,xy+y2-x-y
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a) ĐKXĐ : \(\hept{\begin{cases}x\ne0\\x\ne-2\end{cases}}\)
\(N=\frac{\left(x+2\right)^2}{x}.\left(1-\frac{x^2}{x+2}\right)-\frac{x^2+6x+4}{x}\)
\(N=\frac{\left(x+2\right)^2}{x}.\frac{x+2-x^2}{x+2}-\frac{x^2+6x+4}{x}\)
\(N=\frac{\left(x+2\right)\left(x+2-x^2\right)-x^2-6x-4}{x}\)
\(N=\frac{x^2+2x-x^3+2x+4-2x^2-x^2-6x-4}{x}\)
\(N=\frac{-x^3-2x^2-2x}{x}\)
\(N=\frac{-x\left(x^2+2x+2\right)}{x}\)
\(N=-\left(x^2+2x+2\right)\)
b) \(N=-\left(x^2+2x+2\right)\)
\(\Leftrightarrow N=-\left(x^2+2x+1+1\right)\)
\(\Leftrightarrow N=-\left(x+1\right)^2-1\le-1\)
Max N = -1 \(\Leftrightarrow x=-1\)
Vậy .......................
3(x - 1)2 - (x + 1)2 + 2(x - 3)(x + 3) - (2x + 3)2 - (5 - 20x)
= 3(x2 - 2x + 1) - (x + 1)(x + 1) + 2(x2 - 9) - (2x + 3)(2x + 3) - 5 + 20x
= 3x2 - 6x + 3 - x(x + 1) - 1(x + 1) + 2x2 - 18 - 2x(2x + 3) - 3(2x + 3) - 5 + 20x
= 3x2 - 6x + 3 - x2 - 2x - 1 + 2x2 - 18 - 4x2 - 6x - 6x - 9 - 5 + 20x
= (3x2 - x2 + 2x2 - 4x2) + (-6x - 2x - 6x - 6x + 20x) + (3 - 1 - 18 - 9 - 5)
= -30
=> biểu thức A không phụ thuộc vào x
A = 3( x - 1 )2 - ( x + 1 )2 + 2( x - 3 )( x + 3 ) - ( 2x + 3 )2 - ( 5 - 20x )
A = 3( x2 - 2x + 1 ) - ( x2 + 2x + 1 ) + 2( x2 - 9 ) - ( 4x2 + 12x + 9 ) - 5 + 20x
A = 3x2 - 6x + 3 - x2 - 2x - 1 + 2x2 - 18 - 4x2 - 12x - 9 - 5 + 20x
A = ( 3x2 - x2 + 2x2 - 4x2 ) + ( -6x - 2x - 12x + 20x ) + ( 3 - 1 - 18 - 9 - 5 )
A = -30 ( đpcm )
Pt \(\Leftrightarrow\left(4x-1\right)\sqrt{x^3+1}=2\left(x^3+x\right)+1\)
Đặt \(\sqrt{x^3+1}=i\)
Ta có pt : \(\left(4x-1\right)i=2i^2+1\)
\(\Leftrightarrow2i^2+\left(4x-1\right)i+2x-1=0\Leftrightarrow\orbr{\begin{cases}i=\frac{1}{2}\\i=2x-1\end{cases}}\)
Tới đây tự blabla tiếp:))
mình nghĩ sửa đề bài là \(\frac{\sqrt{x^2-x+6}+7\sqrt{x}-\sqrt{6\left(x^2+5x-2\right)}}{x+3-\sqrt{2\left(x^2+10\right)}}\le0\)
a)\(A=\frac{6}{-2^2-3}\)
Ta có: \(x^2\ge0\Rightarrow2x^2+3\ge3\forall x\Rightarrow-2x^2-3\le-3\)
\(\Rightarrow A\ge-2\Rightarrow MinA=-2\)khi x=0
b) Ta có: \(x^2+2x+6=\left(x+1\right)^2+5\ge5\Rightarrow-x-2x-6\le-5\)
\(\Rightarrow B\ge\frac{-1}{5}\Rightarrow MinB=\frac{-1}{5}\)khi x=-1
c) Ta có:\(10x-x^2+3=-\left(x^2-10x+25\right)+28\le28\)\(\Rightarrow C\ge\frac{7}{28}=\frac{1}{4}\)
c) ĐKXĐ : \(x\ne4\)
Để biểu thức \(\frac{3x^3-4x^2+x-1}{x-4}\) nguyên với \(x\) nguyên thì :
\(3x^3-4x^2+x-1⋮x-4\)
\(\Leftrightarrow3x^3-12x^2+8x^2-32x+33x-132+131⋮x-4\)
\(\Leftrightarrow3x^2.\left(x-4\right)+8x.\left(x-4\right)+31.\left(x-4\right)+131⋮x-4\)
\(\Leftrightarrow131⋮x-4\)
\(\Leftrightarrow x-4\inƯ\left(131\right)\)
\(\Leftrightarrow x-4\in\left\{-1,1,131,-131\right\}\)
\(\Leftrightarrow x\in\left\{3,5,135,-127\right\}\)
d) ĐKXĐ : \(x\ne-\frac{3}{2}\)
Để biểu thức \(\frac{3x^2-x+1}{3x+2}\) nhận giá trị nguyên với \(x\) nguyên thì :
\(3x^2-x+1⋮3x+2\)
\(\Leftrightarrow3x^2+2x-3x-2+3⋮3x+2\)
\(\Leftrightarrow x.\left(3x+2\right)-\left(3x+2\right)+3⋮3x+2\)
\(\Leftrightarrow3⋮3x+2\)
\(\Leftrightarrow3x+2\inƯ\left(3\right)\)
\(\Leftrightarrow3x+2\in\left\{-1,1,-3,3\right\}\)
\(\Leftrightarrow x\in\left\{-1,-\frac{1}{3},-\frac{5}{3},\frac{1}{3}\right\}\) mà \(x\) nguyên
\(\Rightarrow x=-1\)
a) ĐKXĐ : \(x\ne3\)
Để \(\frac{2}{x-3}\)nguyên
=> \(2⋮x-3\)
=> \(x-3\inƯ\left(2\right)=\left\{\pm1;\pm2\right\}\)
x-3 | 1 | -1 | 2 | -2 |
x | 4 | 2 | 5 | 1 |
Cả 4 giá trị đều tmđk
KL : Vậy x = { 4 ; 2 ; 5 ; 1 }
b) ĐKXĐ : \(x\ne-2\)
Để \(\frac{3}{x+2}\)nguyên
=> \(3⋮x+2\)
=> \(x+2\inƯ\left(3\right)=\left\{\pm1;\pm3\right\}\)
x+2 | 1 | -1 | 3 | -3 |
x | -1 | -3 | 1 | -5 |
Cả 4 giá trị đều tmđk
KL : Vậy x = { -1 ; -3 ; 1 ; -5 }
a, ĐKXĐ : \(x\ne3\)
\(\frac{2}{x-3}\)có giá trị nguyên
\(\Leftrightarrow x-3\inƯ\left(2\right)\)
\(Ư\left(2\right)=\left\{\pm1;\pm2\right\}\)
+, TH1 : \(x-3=1\Leftrightarrow x=4\left(TM\right)\)
+, TH2 : \(x-3=-1\Leftrightarrow x=2\left(TM\right)\)
+, TH3 : \(x-3=2\Leftrightarrow x=5\left(TM\right)\)
+, TH4 : \(x-3=-2\Leftrightarrow x=1\left(TM\right)\)
Vậy với \(x\in\left\{4;2;5;1\right\}\)thì \(\frac{2}{x-3}\)có giá trị nguyên
a. \(2x^3+3x^2+2x+3=2x\left(x^2+1\right)+3\left(x^2+1\right)=\left(2x+3\right)\left(x^2+1\right)\)
b. \(a^2-ab+a-b=a\left(a+1\right)-b\left(a+1\right)=\left(a-b\right)\left(a+1\right)\)
c. \(2x^2+4x+2-2y^2=2\left(x^2+2x+1-y^2\right)=2\left(x+1+y\right)\left(x+1-y\right)\)
d. \(x^4-2x^3+10x^2-20x=x\left(x^3-2x^2+10x-20\right)\)
\(==x.x\left(x^2+10\right)-2\left(x^2+10\right)=x\left(x-2\right)\left(x^2+10\right)\)
e. \(x^3+2x^2+x=x^2\left(x+1\right)+x\left(x+1\right)=\left(x^2+x\right)\left(x+1\right)\)
f. \(xy+y^2-x-y=x\left(y-1\right)+y\left(y-1\right)=\left(x+y\right)\left(y-1\right)\)
a) 2x3 + 3x2 + 2x + 3
= ( 2x3 + 2x ) + ( 3x2 + 3 )
= 2x( x2 + 1 ) + 3( x2 + 1 )
= ( x2 + 1 )( 2x + 3 )
b) a2 - ab + a - b
= ( a2 + a ) - ( ab + b )
= a( a + 1 ) - b( a + 1 )
= ( a - b )( a + 1 )
c) 2x2 + 4x + 2 - 2y2
= ( 2x2 - 2y2 ) + ( 4x + 2 )
= 2( x2 - y2 ) + 2( 2x + 1 )
= 2( x2 - y2 + 2x + 1 )
= 2[ ( x2 + 2x + 1 ) - y2 ]
= 2[ ( x + 1 )2 - y2 ]
= 2( x - y + 1 )( x + y + 1 )
d) x4 - 2x3 + 10x2 - 20x
= x( x3 - 2x2 + 10x - 20 )
= x[ ( x3 - 2x2 ) + ( 10x - 20 ) ]
= x[ x2( x - 2 ) + 10( x - 2 ) ]
= x( x - 2 )( x2 + 10 )
e) x3 + 2x2 + x = x( x2 + 2x + 1 ) = x( x + 1 )2
f) xy + y2 - x - y
= ( xy - x ) + ( y2 - y )
= x( y - 1 ) + y( y - 1 )
= ( x + y )( y - 1 )