Resposta:
a)[tex]x=0 \text{ e } x=4[/tex]
b)[tex]x=-3 \text{ e } x=5[/tex]
c)[tex]x=\frac{-1}{3} \text{ e } x=\frac{1}{3}[/tex]
Explicação passo a passo:
a)
[tex]4x-x^{2}=0\\x(4-x)=0\\x=0 \text{ e } x=4[/tex]
b)
[tex]-x^2+2x+15=0\\[/tex]
por Bhaskara
[tex]a=-1 \text{, } b=2 \text{ e } c=15\\\\\Delta=b^2-4\cdot a\cdot c\\\Delta=2^2-4\cdot(-1)\cdot15\\\Delta=4+60\\\Delta=64\\\\\\x=\frac{-b\pm \sqrt\Delta}{2\cdot a}\\\\x_{1}=\frac{-2+\sqrt{64}}{2\cdot (-1)} = \frac{-2+8}{-2}=-3\\\\x_{2}=\frac{-2-\sqrt{64}}{2\cdot(-1)} = \frac{-10}{-2}=5[/tex]
c)
[tex]9x^{2}-1=0\\9x^{2}=1\\x^{2}=\frac{1}{9}\\\\x=\pm\sqrt{\left(\frac{1}{9}\right)}=\pm\frac{\sqrt{1}}{\sqrt{9}}=\pm\frac{1}{3}[/tex]
