exam Maths Puzzle Numerical Ability

Are the following lines parellel, perpendicular, or neither?

L1 through (-4, -7) and (1, 3)
L2 through (2, 6) and (4, 10)

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exam Other Question

I am trying to solve and graph x^2+y^2+4x+2y-20=0.
I came up with (-2,-1) radius 5 but I think something is wrong
Please help if you can.

Find the Half-Life or Doubling Time for the following:

Q=1000e^0.5t

I have no idea where to go with this one. Thank you for any help you can offer.