Question

A quadratic equation is written in four equivalent forms below.

I. y = (x - 4)(x + 6)
II. y = x(x - 4) + 6(x - 4)
III. y = (x + 1)2 - 25
IV. y = x2 + 2x - 24

Which of the forms shown above would be the most useful if attempting to find the y-intercept of the quadratic equation?

Answer 1

IV is the most useful (even though all will work)
To find the y-intercept, take x=0 and substitute it into the equations.

We can see that if x=0, you can very easily observe that option IV reduces to
y = 0 + 0 - 24 = -24.
Hence (0,-24) is the y-intercept