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Why is my C1 Line Intersection answer wrong? How would I do it? watch

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1. I have attached the question to this post, along with my answer.

My method for the intersection was:
Put L1 in the form ax+by+c=0 to substitute in L2
Solve this to get an equation in the form ax+by+c=0
Put that equation in the form y=mx+c

I got the answer (-7,7) and the correct answer was (17/3, 4/3). I don't get where I went wrong. How would I solve this correctly?

Thanks, appreciate it
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2. (Original post by blobbybill)
I have attached the question to this post, along with my answer.

My method for the intersection was:
Put L1 in the form ax+by+c=0 to substitute in L2
Solve this to get an equation in the form ax+by+c=0
Put that equation in the form y=mx+c

I got the answer (-7,7) and the correct answer was (17/3, 4/3). I don't get where I went wrong. How would I solve this correctly?

Thanks, appreciate it
first of all rearrange both l1 and l2 to give y as the subject of formula. SO L1 - y=x/2-3/2 and L2 - y= -2/5x + 18/5. Then make them equal each other so the full equation will be -2/5x +18/5 = x/2 - 3/2. Cancelling down to give x gives you 51/9 which is 17/3 =x Put x back into L1 (or any) and you should cancel down to get y on its own, giving y=4/3

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