Answer: y = -4x^2.
Step-by-step explanation:
The coefficient of the quadratic term tells you how much the graph of the given function is stretched vertically (widen horizontally) compared with the parent function (in this case f(x) = x^2).
These are the cases. Given y = Ax^2, for A ≠ 0,
- if |A| > 1, the function is stretched vertically; this is the graph of Ax^2 is narrower than the graph of the parent function, x^2.
- if |A| < 1, the function is stretched horizontally, this is the graph is wider than the graph of x^2.
The greater |A| the narrower the graph.
That is because for the same x-value, f(x) is further of the y-axis as |A| is greater.
So, you conclude that the function f(x) = - 4x^2 is the narrowest function (it is strectched the most) among the choices.
Of course, you can see it if you draw the graphs of the 4 functions in the same coordinate system.