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differentiation turning points help

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What was your different way?

You said you know a point and a gradient, so the point is (-1,-3), gradient is 9.
Equation of this tangent is: y=9x+6

So what should we do next if we follow your approach?

:confused:

I would then have solved that simultaneously with the curve

I was following a standard route that works with any curve

Given that this is a cubic ... your method is better :smile:

Reply 21

dongonaeatu

Original post by TenOfThem

I would then have solved that simultaneously with the curve

I was following a standard route that works with any curve

Given that this is a cubic ... your method is better :smile:

how do i find the area of the triangle is 8 square units and is what i've done so far correct

Reply 22

TenOfThem

Original post by dongonaeatu

how do i find the area of the triangle is 8 square units and is what i've done so far correct

What are the points in question

Reply 23

dongonaeatu

Original post by TenOfThem

What are the points in question

what

Reply 24

TenOfThem

Original post by dongonaeatu

what

I meant the vertices of the triangle

Once you find these it is just a right angled triangle

Reply 25

dongonaeatu

Original post by TenOfThem

I meant the vertices of the triangle

Once you find these it is just a right angled triangle

i dont understand am i meant to draw out the triangle?

Reply 26

bong

Original post by raheem94

...

Original post by TenOfThem

...

Lol you two are always helping people on these forums... whenever I encounter a problem I want to post it up here, but I either solve it myself or forget it :tongue:

Reply 27

TenOfThem

Original post by dongonaeatu

i dont understand am i meant to draw out the triangle?

You don't need to

You have the axes and then the line you found

Where does that meet the axes

What is the area of that triangle

Reply 28

dongonaeatu

Original post by TenOfThem

I meant the vertices of the triangle

Once you find these it is just a right angled triangle

p coordinates are (1,3) and triangle is from this to x axis and y axis
area of a triangle =base times height/2
so is it 3times1/2

but that doesnt make 8 square units

Reply 29

TenOfThem

Original post by dongonaeatu

p coordinates are (1,3) and triangle is from this to x axis and y axis
area of a triangle =base times height/2
so is it 3times1/2

but that doesnt make 8 square units

You are making a triangle with the axes and the Normal line that you found

Reply 30

dongonaeatu

Original post by TenOfThem

You are making a triangle with the axes and the Normal line that you found

the axes are both 0,0
p is (1,3)
or do i have to use my equation 9y=-x+12
y=4/3
x=12 YES

so 12 times 4/3 all divided by 2 = 8 YES THIS IS RIGHT ISNT IT

Reply 31

TenOfThem

Original post by dongonaeatu

the axes are both 0,0
p is (1,3)
or do i have to use my equation 9y=-x+12
y=4/3
x=12 YES

so 12 times 4/3 all divided by 2 = 8 YES THIS IS RIGHT ISNT IT