What kind of transformation converts the graph of f(x)=x^2+4 into the graph of g(x)=9x^2+4?

Question

The answer options are..

Horizontal stretch

vertical stretch

horizontal shrink

vertical shrink

its asking which one of these transformations/dilations makes the first equation into the second one? Please help me!

Answer 1

vertical stretch or horizontal shrink

the 9 increases the y value by 9 fold over just a 1 for the x^2 coefficient.

stretching the vertical makes the parabola more narrow, which is the same

as shrinking the horizontal

but go with vertical stretch.

Horizontal probably gets reserved for parabolas opening left & right, not to up and down parabolas.