C1: Help on differentiation question

Kill.Me.Now

2

Hey everyone!

Im stuck on this question.

The curve with equation y = ax^2 + bx + c passes through the point (1,2). The gradient of the curve is zero at the point (2,1).
Find the values of a, b and c.

Appreciate any help :smile:

Reply 1

Necro Defain

11

Kill.Me.Now

Hey everyone!

Im stuck on this question.

The curve with equation y = ax^2 + bx + c passes through the point (1,2). The gradient of the curve is zero at the point (2,1).
Find the values of a, b and c.

Appreciate any help :smile:

Okay, the first thing to do is work out dy/dx (ie the gradient of the curve). You know this is 0 at the point (2,1) so that will give you an equation with several variables in.

You also know that it passes through x=1,y=2 so you can stick those into the equation to find a 2nd equation and you also know that it passes through (2,1) as it tells you that above so you stick x=2 and y=1 into the equation to get a 3rd equation, solve them all simultaneously to find values for A,B and C :smile:

Reply 2

marcus123

Kill.Me.Now

Hey everyone!

Im stuck on this question.

The curve with equation y = ax^2 + bx + c passes through the point (1,2). The gradient of the curve is zero at the point (2,1).
Find the values of a, b and c.

Appreciate any help :smile:

4a+2b+c = 1
4a = -b
a+b+c = 2

dy/dx = 2ax + b

away you go
-b+2b+c=1
-4a+c=1
-3a+c=2
-a=-1
a = 1
b = -4
c = 5

Reply 3

marcus123

do u have the answers there ?

Reply 4

Will.M

5

Original post by Huwaina

How did you get-b 2b c=1And -4a c=1-3a c=2 ???
I would appreciate a fast reply...
I have an exam today and i am really stressing out...help me please...

You're 13 years too late.

Reply 5

Haneem

8

Original post by marcus123

do u have the answers there ?

It's us from the future, ww3 was gonna start, we faced at least 5 wildfires, oh, not forgetting a global pandemic, protests, and the possibilities of a country getting wipe off the map + china wanting to rewrite religious books and putting Muslims in concentration camps, global warming worse than ever. and we're still doing the same maths question. <3

Reply 6

asilboi1

1

relax bro a=b

C1: Help on differentiation question

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