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the derivative formula that I got is f'(x)= -6x+1

but none of the answers match my answer

|dw:1436827395674:dw|

|dw:1436827520119:dw|

y = –x + 12

is it 26

could you explain me how you got that answer

did you get the derivative function right

f'(x)= -6x+1
you said you got this, something wrong there

you have to differentiate term by term

never mind I got -2x+3

okay

now you have a slope, then you find a point that belongs on this tangent line

but that doesn't have anything in common to the other answers

how?

|dw:1436828112090:dw|

we know the x coordinate of the point,

now we find the y coordinate of the point and its part of the parabola so

y(2) = ?

|dw:1436828189830:dw|

do we plug it into the original formula or the derivate one?

the derivative formula only tells you the slope at every x value

we want to know the actual y point

so which formula could I use to find the y value?

think about it

maximum

wait no, OMG I feel so ignorant.

y = –x^2 + 3x + 8
this equation of parabola

it gives you a y value for every x value

we know there is an intersection at x=2 so we have to see the y value there

y = –x^2 + 3x + 8
y=-2^2+3*2+8 = 10

x=2,y=10
(2,10)|dw:1436828495281:dw|

I got 10

yes,

now u have a point at the slope of the tangent line through that point

can you solve the equation of the line from here

y=mx+b
m=-1
lets plug in our point to see what b or the y intercept must be
10=-1*2+b
b=

10=-1*2+b
10=-2+b
b=10+2=12

Oh i see I thought it was a 1 to the second power

this is the equation of a line
y=mx+b

yeah, OMG I got it. Thank you so much. Could you help me with one more and thats it?

yeah sure

I already found that C actually has the value, but I don't know how to solve A nor B

|dw:1436829534343:dw|

this is the definition of a derivative

it is the equation to find the slope of a tangent line at x

it arises from taking a secant line where the points are getting closer and closer, lim h--->0

for example take a look at any function f(x)

|dw:1436829711928:dw|

|dw:1436829768720:dw|

okay, I see. I got 7 as the slope of the function

at x=2

|dw:1436829791039:dw|

which is 7 right?

|dw:1436829918175:dw|

well my work is done as long you understand how a derivative comes

its from this very simple concept, the slope of the tangent line at some point

okay than you, I understood the secant and tangent line more.