Find the vertex of the parabola formed by the following quadratic function: y = -3x2 + 12x – 7
(-2,-43)
(2, 5)
(-1, -22)
(1, 2)

Question

Find the vertex of the parabola formed by the following quadratic function: y = -3x2 + 12x – 7 
    (-2,-43) 
   (2, 5) 
   (-1, -22) 
   (1, 2)

sburchette · Answer

The x coordinate of the vertex of a parabola is given by$$\frac{-b}{2a}$$In this parabola, the a=-3 and b=12. Substituting we get, $$\frac{-12}{2(-3)}$$ this simplifies to -12/-6=2 So the x coordinate is 2. Substituting 2 for x will give the y value. -3(2)^2+12(2)-7.  -3(4)+24-7=-7. The vertex is at (2,-7)

anonymous · Answer

the answer is not up there

anonymous · Answer

the first coordinate of the vertex is 2, but the second is 
$$-3(2)^2-12\times 2-7=-12+24-7=12-7=5$$

sburchette · Answer

Oops, messed up my arithmetic. My apologies.

anonymous · Answer

typo in my answer 
$$-3(2)^2+12\times 2-7=-12+24-7=12-7=5$$