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Simultaneous equation help

How would I tackle this question?

Line L1 has the equation y=2x+5
Line L2 has the equation 3x+py=14, where p is a constant.
Find the value of p in the case where
(A) L1 is parallel to L2
(B) L1 is perpendicular to L2

My theory was to change the L2 equation so that it is parallel to L1, say by getting it in the same y=mx+c form and then time timesing and dividing the whole equation by the necessary values so that L2 then has the same m value as L1 (I would then repeat this for (B) but get the gradient to be -1/m).

Is my strategy correct? If someone could point me in the right direction I would be very grateful, thank you :smile:

Reply 1

phoenixsilver

So if they are parallel they will have same gradient, perpendicular they will have -1/m.

Your theory is correct, just rearrange!

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