Question #c5316
1 Answer
Oct 1, 2017
Explanation:
given the equation of a parabola in standard form
∙xy=ax2+bx+cx;a≠0
then the x-coordinate of the vertex which is also the
axis of symmetry is
xvertex=−b2a
f(x)=−x2+4x+7 is in standard form
with a=−1,b=4,c=7
⇒xvertex=−4−2=2
substitute this value into the equation for y-coordinate
⇒yvertex=−4+8+7=11
⇒vertex =(2,11)
axis of symmetry is x=2