SOLUTION: Hey, I'm having trouble with these 3 questions about quadratic equation and I can't do it. Stressing me out very much, are you able to help me please. I'll try write out the que

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Question 861967: Hey,
I'm having trouble with these 3 questions about quadratic equation and I can't do it. Stressing me out very much, are you able to help me please. I'll try write out the question as best as I can.
John likes to play baseball with his friends in the local playing ﬁelds. Last
week John hit his best shot ever. The trajectory of the baseball after he
hit it can be modelled by the quadratic equation
y = −x2/40+31x/40+4/5
where y represents the height in metres of the baseball above the ground,
and x represents the horizontal distance in metres of the baseball from the
position where it was struck by John. Assume that the surface of the
playing ﬁeld is horizontal.
(a) The graph of y = −x2/40+31x/40+4/5 is a parabola.
(i) Is the parabola u-shaped or n-shaped? How can you tell this from
the equation?
(ii) Use algebra to ﬁnd the x-intercepts and y-intercept.
(iii) Find the equation of the axis of symmetry, explaining your
method. Use this information to ﬁnd the coordinates of the
vertex, giving your answers to two decimal places.
Those are the three questions I am really struggling with, if you help me with them be a massive help.
Here is a picture of the question as well just in case if I didn't write it out on the browesr
http://gyazo.com/a87957d7039525702b70d68fc866b309
Many thanks

Answer by ewatrrr(24785) (Show Source):
You can put this solution on YOUR website!

Hi
y=
Parabola opening downward (-1/40) < 0. y-intercept = 4/5
Completing the Square
y=
y=
line of symmetry is x = 31/2 = 15.5 V(15.5, 6.80625)
= 0
x-intercept = 15.5 + = 15.5 + 16.5 = 32