Vertex Form to Standard Form

Which of the following equations is in vertex form?

• f(x) = x² + 6x - 2
• f(x) = (x - 1)² + 2

• y = 9x² - 15x + 21

• y = -3x² - 75x - 4

• y = 9x² + 90x + 221

• y = -3x² - 30x - 79

• y = -5x² - 20x - 30

• y = -5x² - 4x - 10

• y = 25x² + 100x + 90

• y = 25x² - 10x - 30

• A
• B
• C
• D

• A
• B
• C
• D