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\(3x^3+3x^2-3x-9=3\left(x^3+x^2-x-3\right)\)
Check lại đề hộ mình nhé:vv
x 3 - 3 x 2 - 4 x + 12 = x 3 - 3 x 2 - 4 x - 12 = x 2 x - 3 - 4 x - 3 = x - 3 x 2 - 4 = x - 3 x + 2 x - 2
\(=\left(x^2+x\right)^2+4\left(x^2+x\right)+4-16\\ =\left(x^2+x+2\right)^2-16\\ =\left(x^2+x+2-4\right)\left(x^2+x+2+4\right)\\ =\left(x^2+x-2\right)\left(x^2+x+6\right)\\ =\left(x-1\right)\left(x+2\right)\left(x^2+x+6\right)\)
=\(x^4+2x^3+x^2+4x^2+4x-12\)
=\(x^4+2x^3+5x^2+4x-12\)
=\(x^4-x^3+3x^3-3x^2+8x^2+4x-12\)
=\(x^3(x-1)+3x^2(x-1)+4(2x^2+x-3)\)
=\(x^3(x-1)+3x^2(x-1)+4(2x^2-2x+3x-3)\)
=\(x^3(x-1)+3x^2(x-1)+4[2x(x-1)+3(x-1)]\)
=\(x^3(x-1)+3x^2(x-1)+4(x-1)(2x+3)\)
=\((x-1)[x^3+3x^2+4(2x+3)]\)
=\((x-1)(x^3+3x^2+8x+12)\)
\(\left(x^2+x\right)^2+\left(4x^2+4x\right)+4-16\\ =\left(x^2+x+2\right)^2-16\\ =\left(x^2+x+2-4\right)\left(x^2+x+2+4\right)\\ =\left(x^2+x-2\right)\left(x^2+x+6\right)\)
\(x^2+x-2\) vẫn còn phân tích được nữa bạn nhé.
\(x^2+x-2=\left(x-1\right)\left(x+2\right)\)
\(x^2\left(x-3\right)+4\left(3-x\right)\)\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x^2-4\right)\left(x-3\right)\)\(=\left(x-2\right)\left(x+2\right)\left(x-3\right)\)
\(x^2\left(x-3+12-4x\right)\)
\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-4\right)\)
\(=\left(x-3\right)\left(x-2\right)\left(x+2\right)\)
#)Giải :
\(x^3-2x-4\)
\(=x^3+2x^2-2x^2+2x-4x-4\)
\(=x^3+2x^2+2x-2x^2-4x-4\)
\(=x\left(x^2+2x+2\right)-2\left(x^2+2x+2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
\(x^4+2x^3+5x^2+4x-12\)
\(=x^4+x^3+6x^2+x^3+x^2+6x-2x^2-2x-12\)
\(=x^2\left(x^2+x+6\right)+x\left(x^2+x+6\right)-2\left(x^2+x+6\right)\)
\(=\left(x^2+x+6\right)\left(x^2+x-2\right)\)
\(=\left(x^2+x+6\right)\left(x-1\right)\left(x+2\right)\)
Câu 1.
Đoán được nghiệm là 2.Ta giải như sau:
\(x^3-2x-4\)
\(=x^3-2x^2+2x^2-4x+2x-4\)
\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
a) \(2x^2+5x+2\)
\(=2x^2+4x+x+2\)
\(=2x\left(x+2\right)+\left(x+2\right)\)
\(=\left(x+2\right)\left(2x+1\right)\)
b) \(4x^2-4x-9y^2+12y-3\)
\(=\left(4x^2-4x+1\right)-\left(9y^2-12y+4\right)\)
\(=\left(2x-1\right)^2-\left(3y-2\right)^2\)
\(=\left(2x-1+3y-2\right)\left(2x-1-3y+2\right)\)
\(=\left(2x+3y-3\right)\left(2x-3y+1\right)\)
c) \(x^4-2x^3-4x^2+4x-3\)
\(=x^4+x^3-x^2+x-3x^2-3x+3x-3\)
\(=\left(x^4+x^3-x^2+x\right)-\left(3x^2+3x-3x+3\right)\)
\(=x\left(x^3+x^2-x+1\right)-3\left(x^3+x^2-x+1\right)\)
\(=\left(x^3+x^2-x+1\right)\left(x-3\right)\)
d) \(x^3-x+3x^2y+3xy^2+y^3-y\)
\(=\left(x^3+3x^2y+3xy^2+y^3\right)-\left(x+y\right)\)
\(=\left(x+y\right)^3-\left(x+y\right)\)
\(=\left(x+y\right)\left[\left(x+y\right)^2-1\right]\)
\(=\left(x+y\right)\left(x+y-1\right)\left(x+y+1\right)\)
x3-3x2-4x+12=(x3-3x2)-(4x-12)=x2(x-3)-4(x-3)=(x-3)(x2-4)=(x-3)(x-2)(x+2)
\(x^3-3x^2-4x+12\)
\(=\left(x^3-3x^2\right)-\left(4x-12\right)\)
\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-4\right)\)
\(=\left(x-3\right)\left(x-2\right)\left(x+2\right)\)
\(3x^3+19x^2+4x-12=3x^3+3x^2+16x^2+16x-12x-12=3x^2\left(x+1\right)+16x\left(x+1\right)-12\left(x+1\right)=\left(x+1\right)\left(3x^2+16x-12\right)=\left(x+1\right)\left(3x^2+18x-2x-12\right)=\left(x+1\right)\left[3x\left(x+6\right)-2\left(x+6\right)\right]=\left(x+1\right)\left(3x-2\right)\left(x+6\right)\)
3x\(^3\)-19x\(^2\)+4x+12
=3x\(^3\)-3x\(^2\)-16x\(^2\)+16x-12x+12
=3x\(^2\)(x-1)-16x(x-1)-12(x-1)
=(x-1)(3x\(^2\)-16x-12)
=(x-1)(3x\(^2\)-18x+2x-12)
=(x-1)[3x(x-6)+2(x-6)]
=(x-1)(x-6)(3x+2)