Question

for the conic y=5x^2-40x+78 find an equation in standard form and its vertex, focus, and directrix

Answer 1

complete the square
y = 5(x^2 - 8x + ....) + 78
= 5(x^2 - 8x + 16 - 16) + 78
= 5( (x-4)^2 - 16) + 78
= 5(x-4)^2 - 80 + 78
= 5(x-4)^2 - 2

take over ....

Answer 2

What's my next step??

Answer 3

We could write our answer in the form
y+2 = 5(x-4)^2

take a look at
http://jwilson.coe.uga.edu/emt725/class/sarfaty/emt669/instructionalunit/parabolas/parabolas.html
half-way down the page at example 3
and follow the steps.

Answer 4

thank you!