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# Area of the triangle ACP with co-ordinates...: ?

A (1,7), C (0, -15) , P (6, -3)

I got 45cm ^2

but the answer book says 18.5?

The actual question goes (and its the third part of the question), "given that L1 crosses the y-axis at point C calculate the area of (triangle)OCP."

L1: y = 2x - 15

L2: y = -1/2 x

L1 and L2 intersect at P

O is origin

(also, L1 passes through point (3,-9) and has gradient 2)

### 1 Answer

- Anonymous9 years agoFavorite Answer
I get that this triangle has an area of 60 units^2, not 45 cm^2 (as you say) nor 18.5 cm^2 (as the answer the book gives), so your coordinates for A, C, and/or P are wrong or something.

If it is given that L1 passes through (3, -9) and has a gradient of 2, then the equation for L1 is correct. However, what information does the problem give for L2, or is that also given?

With all that said, I am assuming that the equations of L1 and L2 are correct.

Notice that O is a vertex of the triangle, so one vertex will be (0, 0). The other two are (0, -15) and (6, -3) (you found P correctly). I get that this triangle has an area of 45 cm^2 (like your answer).

Can you post the FULL question please?