Algebra 2 practice

Finding the Vertex of a Parabola — Practice

Find the turning point of any parabola — from standard form with x=b2ax = -\frac{b}{2a}, or by reading vertex form directly — with every step explained.

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What you'll practice

The vertex is a parabola's maximum or minimum point, and everything about graphing quadratics hangs off it. From standard form y=ax2+bx+cy = ax^2 + bx + c, the x-coordinate is x=b2ax = -\frac{b}{2a}; substitute back for y. From vertex form y=a(xh)2+ky = a(x-h)^2 + k, the vertex (h,k)(h, k) can be read directly — signs permitting. These questions cover both, plus max/min interpretation.

Worked example

Find the vertex of y=x26x+5y = x^2 - 6x + 5.

  1. x-coordinate: x=b2a=62(1)=3x = -\frac{b}{2a} = -\frac{-6}{2(1)} = 3.
  2. Substitute back: y=(3)26(3)+5=918+5=4y = (3)^2 - 6(3) + 5 = 9 - 18 + 5 = -4.
  3. Vertex: (3,4)(3, -4).
  4. Since a=1>0a = 1 > 0, the parabola opens upward — the vertex is a minimum.

Common mistakes

  • Sign error in b2a-\frac{b}{2a}: with b=6b = -6, the x-coordinate is +3+3, not 3-3.
  • Reading vertex form with the wrong sign: y=(x1)2+7y = (x-1)^2 + 7 has vertex (1,7)(1, 7), not (1,7)(-1, 7) — the form is (xh)(x - h).
  • Stopping after x: the vertex is a point. Substitute back to get the y-coordinate.

Try a few

1. Find the vertex of y=x2+4x+1y = x^2 + 4x + 1.

  • (2,3)(-2, -3)
  • (2,13)(2, 13)
  • (2,1)(-2, 1)
  • (4,1)(-4, 1)

2. Find the vertex of y=2x28x+3y = 2x^2 - 8x + 3.

  • (2,5)(2, -5)
  • (2,27)(-2, 27)
  • (2,3)(2, 3)
  • (4,3)(4, 3)

3. What is the maximum value of y=(x1)2+7y = -(x-1)^2 + 7?

  • 77, at x=1x = 1
  • 77, at x=1x = -1
  • 11, at x=7x = 7
  • It has no maximum

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FAQ

How do you find the vertex from standard form?
Compute x = −b/(2a), then substitute that x back into the equation for y. The vertex is that (x, y) point.
When is the vertex a maximum vs a minimum?
Look at a: if a is positive the parabola opens up and the vertex is a minimum; if a is negative it opens down and the vertex is a maximum.
Is Cramzoo free?
Cramzoo is free to start — every unit opens with free skills and no account is needed. This particular skill is part of Premium ($6/month or $30/year), which unlocks every skill plus the parent progress dashboard.
How is this different from IXL?
No punishing score. A wrong answer gives you a step-by-step explanation, not a number that drops — and every question is reviewed by a human before you see it.

Related Algebra 2 skills

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