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Descompuneti in factori urmatoarele expresii:

a) x³+6x²+9x
b) x la puterea a 4 a-13x³+30x²
c) 3x³-15x
d) 4x la puterea a 5 a-x³
e) x la a 4 a+4
f) x²-9x+14
g) 2x²+5x+3
h) 3x²+7x+4
i) x²-15x+44
j) x²+x-20
k) x la a 4 a+x²+1

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Răspuns :

[tex]a)x^3+6x^2+9=x(x^2+6x+9)=x(x+3)^2\\ b)x^4-13x^3+30x^2=x^2(x^2-13x+30)=x^2(x^2-10x-3x+30)=\\ =x^2[x(x-10)-3(x-10)]=x^2(x-3)(x-10)\\ c)3x^3-15x=3x*(x^2-5)\\ d)4x^5-x^3=x^3(4x^2-1)=x^3(2x-1)(2x+1)\\ [/tex]
[tex]e)x^4+4=x^4+4x^2+4-4x^2=(x^2+2)^2-4x^2=\\ =(x^2+2x+2)(x^2-2x+2)\\ f)x^2-9x+14=x^2-2x-7x+14=x(x-2)-7(x-2)=\\ =(x-2)(x-7)\\ g)2x^2+5x+3=2x^2+2x+3x+3=2x(x+1)+3(x+1)=\\ =(x+1)(2x+3)\\ h)3x^2+7x+4=3x^2+3x+4x+4=3x(x+1)+4(x+1)=\\ =(x+1)(3x+4)\\ i)x^2-15x+44=x^2-11x-4x+44=x(x-11)-4(x-11)=\\ =(x-11)(x-4)\\ j)x^2+x-20=x^2+5x-4x-20=x(x+5)-4(x+5)=\\ =(x+5)(x-4)\\ k)x^4+x^2+1=x^4+2x^2+1-x^2=(x^2+1)-x^2=\\ =(x^2-x+1)(x^2+x+1)[/tex]