For the function f(x) = x2 + 5x - 5, find and simplify the

[marshall1432]

1. For the function f(x) = x2 + 5x - 5, find and simplify the difference quotient:

f(x) - f(1)
------------
x-1

(x2+5x-5) - (1+5-5)
-----------------------
x-1

(x2+5x-5) - (1)
------------------
x-1

now im stuck. i cant find two numbers that multiply to be -5 and add to be 5. the only ones i can think of are the numbers 5 and 1 but that wont work will it?

2. Use your graphing calculator to approximate the point at which the function f(x) = -3x3 + 5x2 - 1 has a local maximum value. Give both coordinates rounded to two decimal places.

i got an error message after i converted it to a y= formula.

3. The perimeter of a rectangle with width x is 50 feet. The function below gives the area of the rectangle as a function of x.
A(x) = -x2 + 25x
Use your graphing calculator to find the value of x which maximizes the area. Round your answer to two decimal places.

the same thing with this one. i got another error message, syntax.

can anyone help me with these 3? thanks

 

[tkhunny]

-5-1 = -6?
Factor the numerator.

 

[skeeter]

Re: help:

1. For the function f(x) = x2 + 5x - 5, find and simplify the difference quotient:

f(x) - f(1)
------------
x-1

(x2+5x-5) - (1+5-5)
-----------------------
x-1

(x2+5x-5) - (1)
------------------
x-1

(x^2 + 5x - 5) - (1) = x^2 + 5x - 6 ... now, factor that and see what cancels

now im stuck. i cant find two numbers that multiply to be -5 and add to be 5. the only ones i can think of are the numbers 5 and 1 but that wont work will it?

2. Use your graphing calculator to approximate the point at which the function f(x) = -3x3 + 5x2 - 1 has a local maximum value. Give both coordinates rounded to two decimal places.

i got an error message after i converted it to a y= formula.

huh? just graph the function Y = -3x^3 + 5x^2 - 1 and look for the coordinates of the tops of any hills you see on th graph ... looks like there's one close to (1,1)

3. The perimeter of a rectangle with width x is 50 feet. The function below gives the area of the rectangle as a function of x.
A(x) = -x2 + 25x
Use your graphing calculator to find the value of x which maximizes the area. Round your answer to two decimal places.

the same thing with this one. i got another error message, syntax.

what are you typing in exactly? how is your graphing window set? what graphing mode are you in? you might need to have a look at your owner's manual.

can anyone help me with these 3? thanks