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a) x3 -2x2 +5x-4
=x3-x2-x2+x+4x-4
=x2(x-1)-x(x-1)+4(x-1)
=(x2-x+4)(x-1)
b) x3-x2+x+3
=x3+x2-2x2-2x+3x+3
=x2(x+1) -2x(x+1)+3(x+1)
=(x2-2x+3)(x+1)
c) 6x3+x2+x+1
=6x3+ 3x2-2x2-x+2x+1
=6x2(x+\(\frac{1}{2}\)) - 2x(x+\(\frac{1}{2}\)) +2(x+\(\frac{1}{2}\))
=(6x2-2x+2) (x+\(\frac{1}{2}\))
=2( 3x2-x+1) (x+\(\frac{1}{2}\))
d) 4x3 + 6x2+4x+1
= 4x3+2x2+4x2+2x+2x+1
= 4x2(x+\(\frac{1}{2}\))+ 4x(x+\(\frac{1}{2}\))+2(x+\(\frac{1}{2}\))
= 2(2x2 +2x+1)( x+\(\frac{1}{2}\))
e) x6 -9x3+8
a)x^2-(a+b)x+ab
= x^2 - ax - bx + ab
= (x^2 - ax) - (bx - ab)
= x(x-a) - b(x-a)
= (x-b)(x-a)
b)7x^3-3xyz-21x^2+9z
=
c)4x+4y-x^2(x+y)
= 4(x + y) - x^2(x+y)
= (4-x^2) (x+y)
= (2-x)(2+x)(x+y)
d) y^2+y-x^2+x
= (y^2 - x^2) + (x+y)
= (y-x)(y+x)+ (x+y)
= (y-x+1) (x+y)
e)4x^2-2x-y^2-y
= [(2x)^2 - y^2] - (2x +y)
= (2x-y)(2x+y) - (2x+y)
= (2x -y -1)(2x+y)
f)9x^2-25y^2-6x+10y
=
\(\left(x^2+x\right)^2-2x^2-2x-15\)
\(=\left(x^2+x\right)^2-\left(2x^2+2x+15\right)\)
\(=\left(x^2+x\right)^2-\left[\left(2x^2+2x\right)+15\right]\)
\(=\left(x^2+x\right)^2-\left[2.\left(x^2+x\right)+15\right]\)
\(=\left(x^2+x\right)^2-2\left(x^2+x\right)-15\) \(\left(1\right)\)
đặt \(x^2+x=t\)
\(\left(1\right)\)\(=\) \(t^2-2t-15\)
\(=\left(t-1\right)^2-16\)
\(=\left(t-1-4\right)\left(t-1+4\right)\)
\(=\left(t-5\right)\left(t+3\right)\)
thay \(t=x^2+x\) ta có
\(\left(1\right)=\left(x^2+x-5\right)\left(x^2+x+3\right)\)
các câu còn lại tương tự nha
học tốt
\(x^8+x^7+1\)
\(=x^8+x^7+x^6-x^6+x^5-x^5+x^4-x^4+x^3-x^3+x^2-x^2+x-xx+1\)
\(=\left(x^8-x^6+x^5-x^3+x^2\right)\)
\(+\left(x^7-x^5+x^4-x^2+x\right)\)
\(+\left(x^6-x^4+x^3-x+1\right)\)
\(=\left(x^2+x+1\right)\left(x^6-x^4+x^3-x+1\right)\)
Bạn tải ứng dụng PhotoMath về nha. Ứng dụng này sẽ giải toán số chi tiết
a) \(x^3-4x^2-12x+27\)
\(=\left(x^3+27\right)-\left(4x^2+12x\right)\)
\(=\left(x+3\right)\left(x^2-3x+9\right)-4x\left(x+3\right)\)
\(=\left(x+3\right)\left(x^2-7x+9\right)\)
b) \(x^3-3x^2-4x+12\)
\(=x^2\left(x-3\right)-4\left(x-3\right)\)
\(=\left(x^2-4\right)\left(x-3\right)\)
\(=\left(x+2\right)\left(x-2\right)\left(x-3\right)\)
a) \(9x^2+6xy+y^2=\left(3x+y\right)^2\)
b) \(6x-9-x^2=-\left(x-3\right)^2\)
d, \(x^8+x^7+1\)
\(=x^8-x^2+x^7-x+x^2+x+1\)
\(=x^2\left(x^6-1\right)+x\left(x^6-1\right)+x^2+x+1\)
\(=x^2\left(x^3-1\right)\left(x^3+1\right)+x\left(x^3-1\right)\left(x^3+1\right)+x^2+x+1\)
\(=\left(x^5+x^2\right)\left(x^3-1\right)+\left(x^4+x\right)\left(x^3-1\right)+x^2+x+1\)
\(=\left(x^3-1\right)\left(x^5+x^4+x^2+x\right)+x^2+x+1\)
\(=\left(x^2+x+1\right)\left(x-1\right)\left(x^5+x^4+x^2+x\right)+x^2+x+1\)
\(=\left(x^2+x+1\right)\left(x^6-x^4+x^3-x\right)+x^2+x+1\)
\(=\left(x^2+x+1\right)\left(x^6-x^4+x^3-x+1\right)\)
c, \(x^4+5x^3-12x^2+5x+1\)
\(=x^4-x^3+6x^3-6x^2-6x^2+6x-x+1\)
\(=x^3\left(x-1\right)+6x^2\left(x-1\right)-6x\left(x-1\right)-\left(x-1\right)\)
\(=\left(x-1\right)\left[x^3+6x^2-6x-1\right]\)
\(=\left(x-1\right)\left[\left(x-1\right)\left(x^2+x+1\right)+6x\left(x-1\right)\right]\)
\(=\left(x-1\right)\left(x-1\right)\left(x^2+7x+1\right)\)
\(=\left(x-1\right)^2.\left(x^2+7x+1\right)\)
a, \(\left(x^2+x-2\right)\left(x^2+9x+18\right)-28\)
\(=\left(x-1\right)\left(x+2\right)\left(x+3\right)\left(x+6\right)-28\)
\(=\left[\left(x-1\right)\left(x+6\right)\right].\left[\left(x+2\right)\left(x+3\right)\right]-28\)
\(=\left(x^2+5x-6\right)\left(x^2+5x+6\right)-28\)
\(=\left(x^2+5x\right)^2-36-28\)
\(=\left(x^2+5x\right)^2-64\)
\(=\left(x^2+5x-8\right)\left(x^2+5x+8\right)\)
b, \(B=\left(x+1\right)^2\left(2x+3\right)-18\)
\(=\left(4x^2+8x+3\right)\left(x^2+2x+1\right)-18\)
Đặt \(x^2+2x+1=t\Rightarrow4x^2+8x+3=4t-1\)
Ta có: \(B=\left(4t-1\right)t-18\)
\(=4t^2-t-18\)
\(=4t^2-9t+8t-18\)
\(=t\left(4t-9\right)+2\left(4t-9\right)\)
\(=\left(4t-9\right)\left(t+2\right)\)
\(=\left(4x^2+8x-5\right)\left(x^2+2x+3\right)\) (vì \(t=x^2+2x+1\)
\(=\left(2x-1\right)\left(2x+5\right)\left(x^2+2x+3\right)\)
Chúc bạn học tốt.