Which relation is a function? a) y2 + 3x = 9 b) y(2x + 4y) = 8 c) x2 + 7x = 7y2 d) yx = x3 + 4x2 + 4x

The first one is a parabola opening sideways so it will not pass the vertical line test
B   not a function as it can be arranged in form  x =  expression in y^2 so it would be a one-to-many relation.

D is a function  because its a parabola which open upwards so it will pass the vertical line test

If gravity is one third on mars then weight also one third on mars