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6 tháng 7 2017

Ta có : 15x3 + 29x2 - 8x - 12

= 15x3 + 30x2 - x2 - 8x - 12

= 15x(x + 2) - (8x + 16) - (x2 - 4)

= 15x(x + 2) - 8(x + 2) - (x - 2)(x + 2)

= (x + 2)(15x - 8 - x + 2)

= (x + 2) (14x - 6)

3 tháng 8 2017

(x+2)(14x-6)

6 tháng 7 2017

\(x^3+9x^2+26x+24\)

\(=x^3+3x^2+6x^2+18x+8x+24\)

\(=\left(x^3+3x^2\right)+\left(6x^2+18x\right)+\left(8x+24\right)\)

\(=x^2\left(x+3\right)+6x\left(x+3\right)+8\left(x+3\right)\)

\(=\left(x+3\right)\left(x^2+6x+8\right)\)

\(=\left(x+3\right)\left(x^2+2x+4x+8\right)\)

\(=\left(x+3\right)\left[\left(x^2+2x\right)+\left(4x+8\right)\right]\)

\(=\left(x+3\right)\left[x\left(x+2\right)+4\left(x+2\right)\right]\)

\(=\left(x+3\right)\left(x+2\right)\left(x+4\right)\)

6 tháng 7 2017

\(15^3+29x^2-8x-12=15x^3+30x^2-x^2-2x-6x-12\)

\(15x^2.\left(x+2\right)-x.\left(x+2\right)-6.\left(x+2\right)\)\(\left(x+2\right).\left(15x^2-x-6\right)\)

\(\left(x+2\right).\left(15x^2-10x+9x-6\right)\)\(\left(x+2\right).\left(3x-2\right).\left(5x+3\right)\)

\(x^3+9x^2+26x+24=x^3+3x^2+6x^2+18x+8x+24\)\(=x.^2\left(x+3\right)+6x.\left(x+3\right)+8.\left(x+3\right)\)\(=\left(x+3\right).\left(x^2+6x+8\right)\)\(\left(x+3\right).\left(x^2+2x+4x+8\right)=\left(x+2\right).\left(x+3\right).\left(x+4\right)\)

6 tháng 7 2017

Ta có : 15x3 + 29x2 - 8x - 12

= 15x3 + 30x2 - x2 - 8x - 12

= 15x(x + 2) - (8x + 16) - (x2 - 4)

= 15x(x + 2) - 8(x + 2) - (x - 2)(x + 2)

= (x + 2)(15x - 8 - x + 2)

= (x + 2) (14x - 6) 

 click zô nha >_<                 

3: \(15x^3+29x^2-8x-12\)

\(=15x^3+30x^2-x^2-2x-6x-12\)

\(=\left(x+2\right)\left(15x^2-x-6\right)\)

\(=\left(x+2\right)\left(15x^2-10x+9x-6\right)\)

\(=\left(x+2\right)\left(3x-2\right)\left(3x+5\right)\)

5: \(x^3+9x^2+26x+24\)

\(=x^3+4x^2+5x^2+20x+6x+24\)

\(=\left(x+4\right)\left(x^2+5x+6\right)\)

\(=\left(x+4\right)\left(x+2\right)\left(x+3\right)\)

29 tháng 12 2016

\(3x^2-5x+2=3x^2-3x-2x+2=3x\left(x-1\right)-2\left(x-1\right)=\left(3x-2\right)\left(x-1\right)\)

29 tháng 12 2016

b.)x^4+5x^3+15x-9 

=x^4-9+5x^3+15x

=(x^2-3)(x^2+3)+5x(x^2+3)

=(x^2+3)(x^2-3+5x)

28 tháng 9 2017

a) x\(^2\)+8x  +15 

=( x\(^2\)+3x) + ( 5x +15)

= x(x+3)+ 5 (x+3)

=(x+3) (x+5)

b)x\(^2\)-4x-12

=( x\(^2\)- 6x) +( 2x -12)

=x(x-6) + 2 (x-6)

=(x - 6) (x+2)

c)9x\(^2\)-6x-24

 =(9x\(^2\)-18x)+ (12x-24)

=9x(x-2) + 12 (x -2 )

=(x-2) (9x+12)

28 tháng 9 2017

a)  \(x^2+8x+15\)

\(=x^2+8x+16-1\)

\(=\left(x^2+8x+16\right)-1\)

\(=\left(x+4\right)^2-1\)

\(=\left(x+4-1\right)\left(x+4+1\right)\)

\(=\left(x+3\right)\left(x+5\right)\)

b) \(x^2-4x-12\)

\(=x^2-4x+4-16\)

\(=\left(x^2-4x+4\right)-4^2\)

\(=\left(x-2\right)^2-4^2\)

\(=\left(x-2-4\right)\left(x-2+4\right)\)

\(=\left(x-6\right)\left(x+2\right)\)

c) \(9x^2-6x-24\)

\(=9x^2-6x+1-25\)

\(=\left(9x^2-6x+1\right)-5^2\)

\(=\left(3x-1\right)^2-5^2\)

\(=\left(3x-1-5\right)\left(3x-1+5\right)\)

\(=\left(3x-6\right)\left(3x+4\right)\)