Resposta:

-3ײ+18×-15=0. (÷ -3).

x² - 6x + 5 = 0.

(x-1). (x-5) = 0

x'=1 , x"=5.

Explicação passo a passo:

Verified answer

[tex] -3x^2+18x-15=0 [/tex]

[tex] a=-3\quad b=18\quad c=-15[/tex]

[tex] \Delta=b^2-4\cdot a\cdot c[/tex]

[tex] \Delta=18^2-4\cdot(-3)\cdot(-15) [/tex]

[tex] \Delta=324-180 [/tex]

[tex] \Delta=144 [/tex]

[tex] x=\dfrac{-b\pm\sqrt\Delta}{2\cdot a}[/tex]

[tex] x=\dfrac{-18\pm\sqrt{144}}{2\cdot(-3)} [/tex]

[tex] x=\dfrac{-18\pm12}{ -6}\begin{cases}x'=\dfrac{-18+12}{-6}=\dfrac{-6}{-6}=1\\\\x''=\dfrac{-18-12}{-6}=\dfrac{-30}{-6}=5\end{cases} [/tex]

[tex]\red{\boldsymbol{ S=\{1~;~5\}}}[/tex]