What is the vertex of $y = - x^{2} + 16 x + 21$ $y= -x^2+16x + 21$ ?

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Answer 1 · 2018-06-30T07:00:48

(8,85)

$\frac{- b}{2 a}$ $(-b)/(2a)$ gives the x coordinate for the vertex

$\frac{- 16}{2 \times - 1} = \frac{- 16}{- 2} = 8$ $(-16)/(2xx-1)=(-16)/(-2)=8$

Put x=8 into the equation

$y = - 8^{2} + 16 \times 8 + 21$ $y=-8^2+16xx8+21$

$y = - 64 + 128 + 21$ $y=-64+128+21$

$y = 85$ $y=85$

What is the vertex of y= -x^2+16x + 21y=−x2+16x+21y= -x^2+16x + 21?