

The domain would be -2, the x-intercept.
Since it’s supplementary the straight line would equal to 180 degrees
4d - 1 + 105 = 180
4d + 104 = 180
4d = 76
d = 19
THe problem is basically telling us: 
where P is the power disappated and V^2 is our voltage squared.

So, for the second example to find the power we simply have to plug k and our voltage back in, so:
2/3(x + 7) = 10. Divide each side by 2/3.
x + 7 = 15. Subtract each side by 7.
x = 8