A way that I use to determine if something is a function or not is to ask whether or now it passes the “vertical line test”. In other words, does an x have two y’s? if we graphed these points, and proceeded to draw a vertical line through it, if it touches the function twice, then it is not a function. So I believe your answers would be A and C (In A, when x is 2, there are two y’s. Same goes with C, when x is 1, 4, 9 etc).
I hope this answer helps! :)
It would be: Kn + 4f = 9
kn = 9 - 4f
n = (9-4f) / K
Hope this helps!
Pythagorean Theorem: a^2 + b^2 = c^2
-A and B are legs of the triangle
-C is the hypotenuse
#1.
6^2 + 8^2 = c^2
36 + 64 = c^2
100 = c^2
c = 10
#2.
5^2 + 12^2 = c^2
25 + 144 = c^2
169 = c^2
c = 13
#4.
10^2 + 4^2 = c^2
100 + 16 = c^2
116 = c^2
c = 
#5.
15^2 + 9^2 = c^2
225 + 81 = c^2
306 = c^2
c = 
#6.
120^2 + b^2 = 150^2
14400 + b^2 = 22500
b^2 = 8100
b = 90
#7.
144^2 + b^2 = 194^2
20736 + b^2 = 37636
b^2 = 16900
b = 130
Hope this helps!! :)