Question

Calc I Problem:
Need some help with these problems, they are test problems that i think i got correct and were marked wrong.

Find the equation of the tangent line to the graph of f(x)=x^2 at the point (2,4).

A.) Find the value of f'(2). You may use the rule in order to find the derivative.
B.) So, the slope of the tangent line is _____.
C.) The equation of the tangent line is f(x) = ____.

Answer 1

what did you answer?

Answer 2

My answers are:
A) f'(2) = 4
B) 2
C) 2x

Answer 3

Monitoring.

Answer 4

oooh..damn so thats why i missed it. but the slope = 2 is correct?

Answer 5

wait, y=2x does work. y= 2*2 = 4

so you are correct.

Answer 6

so the whole answer is correct?

Answer 7

you found the correct f'(2) = 4

how did you get the slope = 2 ( the derivative is the slope)

Answer 8

Well, its asking for the slope when x=2, so although you got the derivative of the equation correct, you did not get the slope when x=2

Answer 9

ooh i just figured that y=2x is the equation so the slope was 2
'y=mx+b'

Answer 10

m=2

Answer 11

there are lots of lines that could go through (2,4)

you want the line that has the *same* slope as the tangent line
i.e. the derivative's value (at x=2)

Answer 12

so the slope would have been 4? :\

Answer 13

yes. The derivative is the "slope" at a *very short section" of the curve

Answer 14

damn alright so thats why i got that wrong.

Answer 15

once you use m=4 you have to find b to answer the last part.

Answer 16

well she gave me partial credit so i guess thats pretty fair. i had it just gave the wrong part for the answer.

Answer 17

alright well that makes sense now, thank you.

Answer 18

yw