1)Phân tích đa thức thành nhân tử:
a) x3-15x2-14x-120
b)x3+15x2+74x+120
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a: \(=5x\left(xy^2+3x+6y^2\right)\)
b: \(=\left(x-2\right)\left(x+3\right)-\left(x-2\right)\left(x+2\right)=\left(x-2\right)\left(x+3-x-2\right)=\left(x-2\right)\)
c: \(=\left(x-3\right)\left(x-4\right)\)
d: \(=x\left(x^2-2xy+y^2-9\right)\)
=x(x-y-3)(x-y+3)
e: \(=\left(x+y\right)^2-25=\left(x+y+5\right)\left(x+y-5\right)\)
f: \(=\left(x-4\right)\left(x+3\right)\)
1a) \(=-\left(x^3-3x^2+3x-1\right)=-\left(x-1\right)^3\)
b) \(=-\left(x^3-3x^2+3x-1\right)=-\left(x-1\right)^3\)
\(a,=-\left(x-1\right)^3\left[=\left(1-x\right)^3\right]\\ b,=\left(1-x\right)^3\)
a. \(x^3+15x^2+75x+125\)\(=x^3+3.x^2.5+3.x.5^2+5^3=\left(x+5\right)^3\)
b. \(x^3-9x^2+27x-27=\)\(x^3-3.x^2.3+3x.3^2-27=\left(x-3\right)^3\)
\(x^4-14x^3+71x^2-154x+120\)
\(=x^4-2x^3-12x^3+24x^2+47x^2-94x-60x+120\)
\(=x^3\left(x-2\right)-12x^2\left(x-2\right)+47x\left(x-2\right)-60\left(x-2\right)\)
\(=\left(x-2\right)\left(x^3-12x^2+47x-60\right)\)
\(=\left(x-2\right)\left(x^3-3x^2-9x^2+27x+20x-60\right)\)
\(=\left(x-2\right)\left[x^2\left(x-3\right)-9x\left(x-3\right)+20\left(x-3\right)\right]\)
\(=\left(x-2\right)\left(x-3\right)\left(x^2-9x+20\right)\)
\(=\left(x-2\right)\left(x-3\right)\left(x^2-4x-5x+20\right)\)
\(=\left(x-2\right)\left(x-3\right)\left[x\left(x-4\right)-5\left(x-4\right)\right]\)
\(=\left(x-2\right)\left(x-3\right)\left(x-4\right)\left(x-5\right)\)
\(81x^2y-27xy^2=27xy\left(3x-y\right)\)
\(2x^3+4x^2-6x=2x\left(x^2+2x-3\right)=2x\left(x+3\right)\left(x-1\right)\)
\(25x^2-10xy+30xy^2=5x\left(5x-2y+6y^2\right)\)
\(27x^3-36xy=9x\left(3x^2-4y\right)\)
\(15x^2+30xy+25xy^2=5x\left(3x+6y+5y^2\right)\)
\(81x^2y-27xy^2==27xy\left(3x-y\right);2x^3+4x^2-6x=2x\left(x^2+2x-3\right)=2x\left(x+3\right)\left(x-1\right);25x^2-10xy+30xy^2=5x\left(5x-2y+6y^2\right);27x^3-36xy=3x\left(9x^2-12y\right);15x^2+30xy+25xy^2=5x\left(3x+6y+5y^2\right)\)
1. \(=3x\left(2x+5\right)\)
2. \(=\left(3x-1\right)\left(3x+1\right)\)
3. \(=\left(x+3\right)^2-y^2=\left(x-y+3\right)\left(x+y+3\right)\)
1, = 3x.(2x + 5)
2. = (3x)2 - 12 = (3x - 1).(3x +1 )
3, =(x2 + 6x + 9) - y2 = (x + 3)2 - y2 =(x + y -3 ). (x - y +3)
\(a,a^4+a^2+1\)
\(=\left(a^2\right)^2+2a^2+1-a^2\)
\(=\left(a^2+1\right)^2-a^2\)
\(=\left(a^2+1-a\right)\left(a^2+1+a\right)\)
\(---\)
\(b,a^4+a^2-2\)
\(=a^4-a^2+2a^2-2\)
\(=a^2\left(a^2-1\right)+2\left(a^2-1\right)\)
\(=\left(a^2-1\right)\left(a^2+2\right)\)
\(=\left(a-1\right)\left(a+1\right)\left(a^2+2\right)\)
\(---\)
\(c,x^3-5x^2-14x\)
\(=x^3+2x^2-7x^2-14x\)
\(=x^2\left(x+2\right)-7x\left(x+2\right)\)
\(=\left(x+2\right)\left(x^2-7x\right)\)
\(=x\left(x+2\right)\left(x-7\right)\)
\(a.a^4+a^2+1\)
\(=\left(a^4+2a^2+1\right)-a^2\)
\(=\left(a^2+1\right)^2-a^2\)
\(=\left(a^2+1+a\right)\left(a^2+1-a\right)\)
\(b.a^4+a^2-2\)
\(=a^4+2a^2-a^2-2\)
\(=a^2\left(a^2+2\right)-\left(a^2-2\right)\)
\(=\left(a^2+2\right)\left(a^2-1\right)\)
\(=\left(a^2+2\right)\left(a-1\right)\left(a+1\right)\)
\(c.x^3-5x^2-14x\)
\(=x^3+2x^2-7x^2-14\)
\(=x^3\left(x+2\right)-7x\left(x+2\right)\)
\(=\left(x^3-7x\right)\left(x+2\right)\)
\(=x\left(x-7x\right)\left(x+2\right)\)
a) \(=6x^2y^2\left(6xy-7\right)\)
b) \(=3xy\left(x^3y+5x-6\right)\)
c) \(=\left(ax+ab\right)-\left(bx+x^2\right)=a\left(b+x\right)-x\left(b+x\right)=\left(a-x\right)\left(b+x\right)\)
d) \(=3\left(2x-1\right)-\left(2x-1\right)^2=\left(2x-1\right)\left(3-2x+1\right)=\left(2x-1\right)\left(4-2x\right)=2\left(2x-1\right)\left(2-x\right)\)
\(a,=6x^2y^2\left(6xy-7\right)\\ b,=3xy\left(x^3y+5x-6\right)\\ c,=x\left(a-x\right)-b\left(a-x\right)=\left(x-b\right)\left(a-x\right)\\ d,=3\left(2x-1\right)-\left(2x-1\right)^2=\left(2x-1\right)\left(3-2x+1\right)=2\left(2-x\right)\left(2x-1\right)\)
b: =x^3+6x^2+9x^2+54x+20x+120
=(x+6)(x^2+9x+20)
=(x+6)(x+4)(x+5)
a: Đa thức này không phân tích được nha bạn