Question

maximum value of f(x)=-6x^2+7x+9?

Answer 1

Are you studying parabolas or derivatives?

Answer 2

parabolas

Answer 3

to find the maximum value find the value of x when\[{d(f(x)) \over dx}=0\], the substitute it in the f(x) to find it

Answer 4

y = -6x^2+7x+9

The x-coordinate of the vertex is - b /(2a) where a is the coefficient of x^2 and b is the coefficient of the x term.

x = -(7) / 2-(6) = 7/12

The corresonding y-value is 6 (7/12)^2 + 7 (7/12) + 9 = 167/24 which is the y-coordinate of the vertex.

167/24 is the maximum value of f(x)

See graph at the link:

http://www.wolframalpha.com/input/?i=y+%3D+-6x%5E2%2B7x%2B9

Answer 5

* x = -(7) / 2-(6) = 7/12
should read

x = -(7) / 2(-6) = (-7)/ (-12) = 7/12