18. s = 5r^2 + 7......making r the subject
s - 7 = 5r^2
(s - 7) / 5 = r^2...by taking the sqrt of both sides, it eliminates the ^2
( sqrt (s-7)/5) = r
19. h = ut - 1/2gt^2....u = 100, t = 1 4/5(or 9/5)...g = 6.4
h = (100)(9/5) - 1/2(6.4)(9/5^2)
h = 180 - 1/2(6.4)(3.24)
h = 180 - 3.2(3.24)
h = 180 - 10.368
h = 169.632 or 169 79/125
20. sorry..do not know this one
It will be 57 because if 9 are nickles in the rest are pennies
Substitute "d" = 2, 3.5 and 5 in the given equation and solve to get the "W" values for the respective days. Then plot the graph using days "d" in the "x" axis and weight "w" in the "y" axis the graph will be most definitely "Linear".
The y-intercept of linear function (f- g)(x) is (0,9)
<h3>How to determine the y-intercept?</h3>
The table of values is given as:
x -6 -4 -1 3 4
f(x) 15 11 5 -3 -5
g(x) -36 -26 -11 9 14
The equations of the functions is calculated using:

So, we have:

Evaluate
f(x) = -2x + 3
Also, we have:

Evaluate
g(x) = 5x - 6
Next, we calculate (f - g)(x) using:
(f - g)(x) = f(x) - g(x)
This gives
(f - g)(x) = -2x + 3 - 5x + 6
Substitute 0 for x
(f - g)(0) = -2(0) + 3 - 5(0) + 6
Evaluate
(f - g)(0) = 9
Hence, the y-intercept of (f- g)(x) is (0,9)
Read more about linear functions at:
brainly.com/question/24896196
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