[tex]\displaystyle \sf f(x)=ax^2+bx \ \ ;\ \ V = (1,-2) \\\\ Temos : \\\\\ X_v=\frac{-b}{2a} \\\\ \frac{-b}{2a}= 1 \to -b=2a \to b = -2a \\\\ Da{\'i}} : \\\\ f(x) = ax^2-2ax \\\\ f(1) = -2 \to a-2a = -2 \to -a=-2 \to \boxed{\sf a =2 }\\\\ b = -2a \to \boxed{\sf b = -4 }\\\\ Da{\'i}} ; \\\\ f(x) = 2x^2-4x \\\\ \text{substituindo os pontos : } \\\\[/tex]
[tex]\sf f(-2) = 12 \to 2\cdot (-2)^2 -4\cdot (-2) = 12 \to 8+8=12 \ (FALSO) \\\\ f(-1) = 6 \to 2\cdot(-1)^2-4\cdot(-1) = 6 \to 2+4= 6 (VERDADEIRO) \\\\ f(3) = 8 \to 2\cdot 3^2-4\cdot 3 = 8 \to 18-12 = 8\ ( FALSO)\\\\ f(4) = 16 \to 2\cdot 4^2 - 4 \cdot4 = 16 \to 32-16 = 16 \ (VERDEIRO)[/tex]
letra b
