So the question is asking why x=y2-5y is not a function but x=y2-5y is not. The question also says to substitute -6 with x to solve for 1. (the 2 is an exponent just so you know). I solved y=66 in the first one, but got -1 for the second...??

1) x = y^2 - 5y , x = - 6

- 6 = y^2 - 5y

y^2 - 5y + 6 = 0

(y - 2)(y - 3) = 0 , factorise

y-2 = 0 or y - 3 = 0

y = 2 , y = 3

( -6 , 2 ) & ( -6 , 3 ) are the points

- 6 has two images 2 & 3

not a function as x cannot have two different images

2) y = x^2 - 5

x = - 1

y = ( - 1)^2 - 5

y = 1 - 5 = - 4

(- 1 , - 4 )

- 1 has only one image so it's a function

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