Yes you got it right because the formula is y=mx+b and the m is your slope.
I believe it is 8x.
Use the formula A=1/2(b*h)
A=1/2(4x(5x-1))
A=1/2(20x-4x)
A=1/2(16x)
A=8x
No. It's rational. The solutions are +10 and -10.
C. 2 : 1, because the original ratio would be 8 : 4, but to get it to the correct ratio you must simplify the ratio to 2 : 1.
You would need to use the pythagorean theorum which is would be 8 squared +x squared = 15 squared