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a fost răspuns

Descompuneti in factori expresiile:
a)16(2x-7)²-9(x-3)²;
b)x³-9x²-9x+81;
c)x²-5x-24

Răspuns :

Cristinatibulca
a²-b²=(a-b)(a+b)
[4(2x-7)-3(x-3)][4(2x-7)+3(x-3)]=[8x-28-3x+9][8x-28+3x-9]=(5x-19)(11x-37)

x²-9x²-9x+81=x²(x-9)-9(x-9)=(x-9)(x²-9)=(x-9)(x-3)(x+3)

x²-5x-24=x²-8x+3x-24=x(x-8)+3(x-8)=(x-8)(x+3)

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