You can not work out it unless provided initial distance between the house and shoreline.
the greatest common factor is 2
45 90
/ \ / \
5 9 45 2
/ \ / \
3 3 5 9
5x3x3 / \
3 3
2x5x3x3
Make them both improper fractions.
77/10 - 19/5
Give them common denominators (multiply the second fraction by 2)
77/10 - 38/10
Subtract
39/10 = 3 9/10
To get the extrema, derive the function.
You get y' = 2x^-1/3 - 2.
Set this equal to zero, and you get x=0 as the location of a critical point.
Since you are on a closed interval [-1, 1], those points can also have an extrema.
Your min is right, but the max isn't at (1,1). At x=-1, you get y=5 (y = 3(-1)^2/3 -2(-1); (-1)^2/3 = 1, not -1).
Thus, the maximum is at (-1, 5).