Posted by **Andrea** on Tuesday, October 31, 2006 at 8:07pm.

I'm having some troubles with these. Thanks in advance.

If a>0 find the minimum value. If a<0 find the maximum value.

1. y=-x²+2x+5

2. y=-2x²-3x+4

These are functions for parabolas, so

f(x)=ax²+bx+c when a does not equal 0

In both your examples, the "a", which is the coefficient of the x^2 term, is negative.

1. dy/dx = -2x + 2, and that equals zero at a maximum or minimum. So the maximum would occur at x=1.

d2y/dx^2 = -2. Since that is always negative, x=1 is a point of maximum value.

Do #2 similarly.

Thank-you, but I really don't understand what you mean by dy/dx. I'm feeling terribly stupid, but nothing like that is in my book.

Find Minimum or maximum value of f(x)=2x^2 + 3x -9

## Answer This Question

## Related Questions

- Algebra- Maximum and minimum. - I dont understand how to find the maximum and ...
- math - Maximum or minimum values of the function f(x) = (1 – x)^2 e^x is: i need...
- math - Determine whether the given quadratic function has a minimum value or ...
- Math - 1.What is the smallest possible value of 2x^4+(8/x^4) over all real ...
- math - Determine whether this function has a mzximum or minimum value and then ...
- Maximum and Minimum - Its been awhile since I have done compleating the square, ...
- algebra - given the following quadratic equation, determine if it has a maximum ...
- Math - How to find coordinates of vertex, and find out if the function has ...
- Minimum and maximum value - Let f(x) be a decreasing the function defined for x...
- math - find the vertex, the line of symmetry and the maximum or minimum value of...

More Related Questions