A function is defined by . What is the minimum value of ?
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Complete the square: f(x)=(x+2)^2-9, so the minimum is -9. E.
Yes! That's the fastest way. Vertex form makes it obvious.
Ah, I tried using -b/2a and got x=-2 but wasn't sure what to do next. Thanks!
Wait, why isn't the minimum just -5? That's the y-intercept when x=0. I keep getting confused between the y-intercept and the vertex.
The y-intercept is just one point on the parabola. Since the parabola opens upward, there's a lower point at the vertex.
Plug x=-2 and compare to x=0. That cleared it up for me.
The middle choices got me. I narrowed it to -8 and -9 and guessed wrong on my first try.
Classic trap. Always double-check by plugging the vertex x back into the original function.
Solid 605-655 level question. Tests whether you actually know vertex form or just memorize formulas.
What it tests
Your ability to evaluate and compose functions, including unusual defined operations.
Common trap
Applying function operations in the wrong order or ignoring domain restrictions.