## mathtard Group Title Find the vertex f(x)= 3x^2-18x+3 please help me. Awards will be given 3 years ago 3 years ago

1. satellite73

use the all mighty formula $x= -\frac{b}{2a}$ to find the first coordinate

2. satellite73

in this case $a=3,b=-18$ so $-\frac{b}{2a}=-\frac{-18}{2\times3}=3$

3. satellite73

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

4. satellite73

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

5. satellite73

vertex is (3,-24) unless i messed up

6. mathtard

so (3,-24) ? and that would make it a maximum right?

7. satellite73

heck no

8. satellite73

this is a parabola that faces up. no max, but a min

9. satellite73

|dw:1314675140476:dw|

10. satellite73

the minimum value is -24

11. mathtard

Ah I got it mixed up!

12. mathtard

I always do that with the minimum maximum.