Question

I don't really want the answer I just want to know how to find it. I know to use -b / 2a already..
Find the axis of symmetry of the parabola formed by the following quadratic function: y = -5x^2 + 7x - 9
A. x = -7/5
B. x = 7/5
C. x = -7/10
D. x = 7/10
But when I put in a (-5) and b -(7) I get
-(7) / 2 (-5) -(7) / -10 = .7 ? And if I put that in to get y, y also will be a decimal (6.55) ?
Clearly I'm doing something wrong I just don't know what. Thanks for any help.

Answer 1

-(7) / 2 (-5) -(7) / -10 = .7

Answer 2

but then where ever you see the "x" in the formula:
y = -5x^2 + 7x - 9
you plug .7 into it.

Answer 3

I get that, but when I put in .7 I get -6.55. I understand how to do the math, but the answers I get don't go with the answers it wants me to get.. Like how would I get 7/5, 7/10, etc. I thought it would just be x = .7 and y = -6.55. Sorry I'm confused lol.

Answer 4

the axis of symmetry is x = 0.7 or x = 7/10 which is D

Answer 5

Oh so I don't have to plug in for a y, sorry I was just over thinking it, Thank you lol.

Answer 6

right - it just asks for the center of symmetry

Answer 7

the graph will be a parabola opening downwards ( because of negative coefficient of x^2)