Answer:
y = 3/8x
or
3/8 cups of sugar for every 1/2 batch of muffins
Step-by-step explanation:
Since we are only making 1/2 of the full batch of muffins, we only need to use 1/2 the cups of sugar:
cups of sugar.
The "meter" is a larger unit than the "centimeter." Every time you need to convert a larger metric unit to a smaller one, you must multiply to find a greater value.
Since
is the square of x and 6x is twice the product between x and 3, the second square must be 3 squared, i.e. 9.
So, if we think of 15 as 9+6, we have

Which is the required vertex form. This form tells us imediately that the vertex is the point (3,6).
Since the leading coefficient is 1, the parabola is facing upwards (it's U shaped), so the vertex is a minimum.