year 1 differentiation

[pine crescent]

for part b how do we know to differentiate from first principles

like what is kind of the trigger to know to use first principles

is it for when we want the gradient of like a section of the curve

[delicate tusk]

wdym for part b?

you know the coordinates of the 2 points

you dont need differentiation

just use y-y1 = m(x-x1)

you know both of the coordinates

[pine crescent]

u dont know y of second one

[delicate tusk]

sub it into the 3x^2 - 2?

it lies on the curve so you can just sub it into the equation

to get the y

[pine crescent]

wouldnt we get 2 negative solutions tho

which cant be the case

[delicate tusk]

no negative solution?

[pine crescent]

like when u sub it in

u get a quadratic in terms of h

and it gives 2 negative solutions

[delicate tusk]

but then it cancels out

look in the mark scheme

they expanded it

and everything cancels out in the end

so you dont need to worry about negative solutions

[pine crescent]

ohh it just looked like first principles but they just doing y2-y1/x2-1

[delicate tusk]

yeh exactly

[pine crescent]

yh mb i was just confused

[delicate tusk]

yeh nw as long as you understand now