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a: \(x^2+12x+36=0\)
=>\(x^2+2\cdot x\cdot6+6^2=0\)
=>\(\left(x+6\right)^2=0\)
=>x+6=0
=>x=-6
b: \(4x^2-4x+1=0\)
=>\(\left(2x\right)^2-2\cdot2x\cdot1+1^2=0\)
=>\(\left(2x-1\right)^2=0\)
=>2x-1=0
=>2x=1
=>x=1/2
c: \(x^3+6x^2+12x+8=0\)
=>\(x^3+3\cdot x^2\cdot2+3\cdot x\cdot2^2+2^3=0\)
=>\(\left(x+2\right)^3=0\)
=>x+2=0
=>x=-2
a) nhận xét hệ số : 1 + 4 - 29 + 24 = 0
=> x3 + 4x2 - 29x + 24 = x2(x-1) + 5x(x-1) - 24(x-1)
= (x-1)(x2+5x-24) = (x-1)(x-3)(x+8)
b) ...
a) \(x^3+4x^2-29x+24\)=\(\left(x+8\right)\left(x^2-4x+3\right)\)=\(\left(x+8\right)\left(x^2-x-3x+3\right)\)=\(\left(x+8\right)\left(x-1\right)\left(x-3\right)\)
b) \(x^4+6x^3+7x^2-6x+1\)=\(x^4+3x^3-x^2+3x^3+9x^2-3x-x^2-3x+1\)=\(x^2\left(x^2+3x-1\right)+3x\left(x^2+3x-1\right)-\left(x^2+3x-1\right)\)=\(\left(x^2+3x-1\right)\left(x^2+3x-1\right)\)=\(\left(x^2+3x-1\right)^2\)
A,
x^2 - y^2 -2x -2y
= (x^2 - y^2) -(2x +2y)
= (x+y)(x-y) -2(x+y)
= (x+y)(x-y-2)
B,
5x^6 - 320
=5(x^6 - 64)
=5( (x^3)^2 - 8^2)
= 5( x^3 - 8)(x^3+8)
=5(x-2)(x^2 + 2x+4)(x+2)(x^2-2x-4)
\(P\left(x\right)=6x^3+13x^2+4x-3\)
\(=\left(6x^3+6x^2\right)+\left(7x^2+7x\right)-\left(3x-3\right)\)
\(=6x^2\left(x+1\right)+7x\left(x+1\right)-3\left(x+1\right)\)
\(=\left(6x^2+7x-3\right)\left(x+1\right)\)
\(=\left[\left(6x^2-2x\right)+\left(9x-3\right)\right]\left(x+1\right)\)
\(=\left[2x\left(3x-1\right)+3\left(3x-1\right)\right]\left(x+1\right)\)
\(=\left(3x-1\right)\left(2x+3\right)\left(x+1\right)\)
( x2 - 3x )2 + ( 2x2 - 6x ) - 24
= ( x2 - 3x )2 + 2( x2 - 3x ) - 24 (*)
Đặt t = x2 - 3x
(*) trở thành :
t2 + 2t - 24
= t2 - 4t + 6t - 24
= t( t - 4 ) + 6( t - 4 )
= ( t - 4 )( t + 6 )
= ( x2 - 3x - 4 )( x2 - 3x + 6 )
= ( x2 + x - 4x - 4 )( x2 - 3x + 6 )
= [ x( x + 1 ) - 4( x + 1 ) ]( x2 - 3x + 6 )
= ( x + 1 )( x - 4 )( x2 - 3x + 6 )
\(\left(x^2-3x\right)^2+\left(2x^2-6x\right)-24\)
\(=\left(x^2-3x\right)^2+2\left(x^2-3x\right)-24\)(1)
Đặt \(a=x^2-3x\)
(1)=\(a^2+2a-24\)
\(=a^2-4a+6a-24\)
\(=a\left(a-4\right)+6\left(a-4\right)\)
\(=\left(a-4\right)\left(a+6\right)\)
\(=\left(x^2-3x-4\right)\left(x^2-3x+6\right)\)
\(=\left(x^2-4x+x-4\right)\left(x^2-3x+6\right)\)
\(=\left[x\left(x-4\right)+\left(x-4\right)\right]\left(x^2-3x+6\right)\)
\(=\left(x+1\right)\left(x-4\right)\left(x^2-3x+6\right)\)
\(12x-9-4x^2=-\left(2x-3\right)^2\\ Sửa:x^3-6x^2y+12xy^2-8y^3=\left(x-2y\right)^3\)
a,\(=x^3-x^2+5x^2-5x-24x+24\)
\(=x^2\left(x-1\right)+5x\left(x-1\right)-24\left(x-1\right)\)
\(=\left(x-1\right)\left(x^2+5x-24\right)\)
\(=\left(x-1\right)\left(x^2-3x+8x-24\right)\)
\(=\left(x-1\right)\left(x\left(x-3\right)+8\left(x-3\right)\right)\)
\(=\left(x-1\right)\left(x-3\right)\left(x+8\right)\)
x2 - 6x - 4x + 24 = 0
( x2 - 6x ) - ( 4x - 24 ) = 0
x( x - 6 ) - 4 ( x - 6 ) = 0
( x - 4 ) ( x - 6 ) = 0
\(\Rightarrow\orbr{\begin{cases}x-4=0\Rightarrow x=4\\x-6=0\Rightarrow x=6\end{cases}}\)
Vay x= 4 hoac x = 6
x2 - 6x - 4x + 24 = 0
( x2 - 6x ) - ( 4x - 24 ) = 0
x ( x - 6 ) - 4 ( x - 6 ) = 0
( x - 4 ) ( x - 6 ) = 0
\(\Rightarrow\orbr{\begin{cases}x-4=0\\x-6=0\end{cases}}\)
1. x - 4 = 0 => x = 4
2. x - 6 = 0 => x = 6