Question

Descompusa in factori expresia x la puterea a doua- 2x-15 este?

Answer 1

x² - 2 x - 15 = x² - 2 x - 9 - 6 = ( x² - 9 ) - 2 ( x + 3) = ( x + 3 ) ( x - 3 ) - 2 ( x + 3) =

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

Answer 2

x²-2x-15=0

Δ=b²-4ac=4-4·(-15)=4+60=64

x₁=(2+8)/2=5

x₂=(2-8)/2=-3

a(x-x₁)((x-x₂)=(x-5)(x+3)