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Help on some easy C1!

Ok this is the Question:

11. The curve C has equation: y= 9-4x-8/x

The point P on C has x-coordinate equal to 2.

(a) Show that the equation of the tangent to C at the point P is y = 1 – 2x.

(b) Find an equation of the normal to C at the point P.

The tangent at P meets the x-axis at A and the normal at P meets the x-axis at B.

(c) Find the area of triangle APB.

Now I can do all of them apart from part (C). What shall I do there, I've run out of ideas!

Reply 1

samiz20891

you'll now the two values of A and B as that where it crosses the x axis so that should be ok and point P has an x coord of 2 so now you can use 1/2*b*h as you know the end points of the triangle.
Hope that helps

Reply 2

kirky743

Ill have a go and see what i get =)

Reply 3

kirky743

Oh dear its not going well i keep getting y=4x + 11 as the equation of the tangent.... now what am i doing wrong aha?

Reply 4

kirky743

Okay im not having a clever day but i got 11.25?

Reply 5

Ultimate1

kirky743

Okay im not having a clever day but i got 11.25?

Yep thats the asnwer. How'd you get it mate?

Reply 6

kirky743

Reet okay well to get A and B you put y=0 into the respective equations to get your value for x, so then you have A and B.

Draw a diagram if it helps.

A and B will both be on the x axis, so you can use the difference in their x co-ordinates to get your base value.

P is -3 down from the x axis so this is your height.

Then multiply height by base by a half.

That make any sense? Im not too good at explaining things =S