Asked by catherine

Suppose that f (x) is a function such that the relationship given below is true.
f (3 + h) - f (3) = 9h^2 + 8h



What is the slope of the secant line through (3, f (3)) and (7, f (7))?

I am stuck on this one , tried every thing in the world. i don't know how to do it since there is no f(x) given.. so please be descriptive if you help. This is due tomorrow that's why i am posting it again, don't mean to spam.

Answers

Answered by TutorCat
please show your work. maybe myself or the other tutors could figure out what you did wrong.
Answered by catherine
ok. this question also had a part a) which was

(a) What is f '(3)?
so i just divided
(9h^2+8h)/h

(h(9h+8))/h and plugged in 0 since lim->0

got 8 as my answer.

now for B)

i tried plugging 3 into (h) in func 9h^2+8h/h

did same with 7 and got wrong answer. i tried many different ways but kept getting wrong answer.

what i am confused is with how to find values for f(7) and f(3) since there is no function given to begin with...
Answered by MathMate
There is no limitation on the value/size of h, so h can be any number.

f (3 + h) - f (3) = 9h^2 + 8h
so
f(3+h) = 9h^2 + 8h - f (3)
Try setting h=4 to see what you get.
Answered by MathMate
Sorry, the equation should read:
f(3+h) = 9h^2 + 8h + f (3)
Answered by MathMate
In fact, the solution is simpler than that.
Remember TutorCat said:
for the secant:
[f(7)-f(3)]/(7-3)
you can work out
[f(7)-f(3)]
from
f (3 + h) - f (3) = 9h^2 + 8h
by putting h=?

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