mathtard
Find the vertex
f(x)= 3x^2-18x+3
please help me. Awards will be given
Delete
Share
This Question is Closed
anonymous
Best Response
You've already chosen the best response.
0
use the all mighty formula
\[x=
-\frac{b}{2a}\] to find the first coordinate
anonymous
Best Response
You've already chosen the best response.
0
in this case
\[a=3,b=-18\] so
\[-\frac{b}{2a}=-\frac{-18}{2\times3}=3\]
anonymous
Best Response
You've already chosen the best response.
0
that is the first coordinate and the second coordinate is what you get when you replace x by 3. you get
\[3\times 3^2-18\times 3+3=27-54+3=-27+3=-24\] check my arithmetic because it is late
anonymous
Best Response
You've already chosen the best response.
0
also because i didn't really compute. as soon as i saw 27 i knew the next one would be -54. always works that way
anonymous
Best Response
You've already chosen the best response.
0
vertex is (3,-24) unless i messed up
mathtard
Best Response
You've already chosen the best response.
0
so (3,-24) ? and that would make it a maximum right?
anonymous
Best Response
You've already chosen the best response.
0
heck no
anonymous
Best Response
You've already chosen the best response.
0
this is a parabola that faces up. no max, but a min
anonymous
Best Response
You've already chosen the best response.
0
|dw:1314675140476:dw|
anonymous
Best Response
You've already chosen the best response.
0
the minimum value is -24
mathtard
Best Response
You've already chosen the best response.
0
Ah I got it mixed up!
mathtard
Best Response
You've already chosen the best response.
0
I always do that with the minimum maximum.