phân tích đa thức thành nhân tử :
2x2 - 3x -2
3x2 + x -2
4x2 -7x -2
4x2 + 5x -6
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\(\left(x^2+x\right)^2+4x^2+4x-12=\left[\left(x^2+x\right)^2+4\left(x^2+x\right)+4\right]-16=\left(x^2+x+2\right)-4^2=\left(x^2+x+2-4\right)\left(x^2+x+2+4\right)=\left(x^2+x-2\right)\left(x^2+x+6\right)=\left(x-1\right)\left(x+2\right)\left(x^2+x+6\right)\)
\(\left(x^2+x\right)^2+4x^2+4x-12\\ =\left(x^2+x+2\right)-4\\ =\left(x^2+x-2\right)\left(x^2+x+6\right)\)
4x2 - 8x + 3
= 4x2 - 6x - 2x + 3
= ( 4x2 - 6x ) - ( 2x - 3 )
= 2x( 2x - 3 ) - ( 2x - 3 )
= ( 2x - 3 )( 2x - 1 )
\(\left(x^2-5x\right)^2-3x^2+15x-18\)
\(=\left(x^2-5x\right)^2-3\left(x^2-5x\right)-18\)
\(=\left(x^2-5x-6\right)\left(x^2-5x+3\right)\)
\(=\left(x^2-5x+3\right)\left(x-6\right)\left(x+1\right)\)
\(=\left(x^2-5x\right)^2-3\left(x^2-5x\right)-18\\ =\left(x^2-5x\right)^2-6\left(x^2-5x\right)+3\left(x^2-5x\right)-18\\ =\left(x^2-5x\right)\left(x^2-5x-6\right)+3\left(x^2-5x-6\right)\\ =\left(x^2-5x+3\right)\left(x^2-5x-6\right)\\ =\left(x-6\right)\left(x+1\right)\left(x^2-5x+3\right)\)
\(=\left(x^2+5x+8\right)\left(x^2+4x+2x+8\right)=\left(x^2+5x+8\right)\left[x\left(x+4\right)+2\left(x+4\right)\right]\)
\(=\left(x^2+5x+8\right)\left(x+2\right)\left(x+4\right)\)
\(\left(x^2+4x+8\right)^2+3x\left(x^2+4x+8\right)+2x^2=\left(x^2+4x+8\right)^2+2x\left(x^2+4x+8\right)+x\left(x^2+4x+8\right)+2x^2\)
\(=\left(x^2+4x+8\right)\left(x^2+4x+8+2x\right)+x\left(x^2+4x+8+2x\right)\)
\(=\left(x^2+4x+8\right)\left(x^2+6x+8\right)+x\left(x^2+6x+8\right)\)
\(=\left(x^2+4x+8+x\right)\left(x^2+6x+8\right)=\left(x^2+5x+8\right)\left(x^2+6x+8\right)\)
a) x2+x-2
= x2-x+2x-2
= x(x-1)+2(x-1)
= (x+2)(x-1)
b) 2x2+5x+3
= 2x2+2x+3x+3
= 2x(x+1)+3(x+1)
= (2x+3)(x+1)
c) 3x2+5x-2
= 3x2+6x-1x-2
= 3x(x+2)-1(x+2)
= (3x-1)(x+2)
\(2x^2+x-6\)
\(=2x^2-3x+4x-6\)
\(=x\left(2x-3\right)+2\left(2x-3\right)\)
\(=\left(2x-3\right)\left(x+2\right)\)
Đa thức này không phân tích được thành nhân tử.
Bạn coi lại đề.
Ta có: \(4\left(x+5\right)\left(x+6\right)\left(x+10\right)\left(x+12\right)+3x^2\)
\(=4\left(x^2+60+17x\right)\left(x^2+60x+16x\right)+3x^2\)
\(=4\left[\left(x^2+60\right)^2+33x\left(x^2+60\right)+272x^2\right]+3x^2\)
\(=4\left(x^2+60\right)^2+132x\left(x^2+60\right)+1091x^2\)
\(5x^2-4\left(x^2-2x+1\right)-5=\left(5x^2-5\right)-4\left(x-1\right)^2=5\left(x^2-1\right)-4\left(x-1\right)^2=5\left(x-1\right)\left(x+1\right)-4\left(x-1\right)^2=\left(x-1\right)\left[5\left(x+1\right)-4\left(x-1\right)\right]=\left(x-1\right)\left(5x+5-4x+4\right)=\left(x-1\right)\left(x+9\right)\)
a)\(2x^2-3x-2\)
\(=2x^2+x-4x-2\)
\(=x\left(2x+1\right)-2\left(2x+1\right)\)
\(=\left(x-2\right)\left(2x+1\right)\)
b)\(3x^2+x-2\)
\(=3x^2-2x+3x-2\)
\(=x\left(3x-2\right)+\left(3x-2\right)\)
\(=\left(x+1\right)\left(3x-2\right)\)
c)\(4x^2-7x-2\)
\(=4x^2+x-8x-2\)
\(=x\left(4x+1\right)-2\left(4x+1\right)\)
\(=\left(x-2\right)\left(4x+1\right)\)
d)\(4x^2+5x-6\)
\(=4x^2-3x+8x-6\)
\(=x\left(4x-3\right)+2\left(4x-3\right)\)
\(=\left(x+2\right)\left(4x-3\right)\)
ý 1:
2x2-3x-2=2x2-4x+x-2=2x(x-2)+(x-2)=(x-2)(2x+1)
ý 2:
3x2+x-2=3x2+3x-2x-2=(3x2+3x)-(2x+2)=3x(x+1)-2(x+1)=(x+1)(3x-2)
ý 3:
4x2-7x-2=4x2-8x+x-2=(4x2-8x)+(x-2)=4x(x-2)+(x-2)=(x-2)(4x+1)
ý 4:
4x2+5x-6=4x2+8x-3x-6=(4x2+8x)-(3x+6)=4x(x+2)-3(x+2)=(x+2)(4x-3)