Quadratics Day 04 - Finding the Axis of Symmetry

Let's practice finding the axis of symmetry using only equations. Ready?

• Yes!

• I guess.

• Eh.

• Let's just get it over with Ms. Lyons.

First things first. Which of the following equations matches standard form of a quadratic?

• ax + by = c

• y = a(x - h)² + k

• y = ax² + bx + c

• y = mx + b

Great! All quadratic equations look like  $y=ax^2+bx+c$ . Those letters, a, b, and c appear as numbers. They can be used to solve for the A.O.S. and the VERTEX. 

• Got it. 

• Cool.

What is a, b, and c in this equation?  $y=3x^2-5x+4$  

• a = 3, b = -5, c = 4

• a = 3, b = 5, c = 4

• a = 3, b = 5, c = -4

• a = 3, b = -5, c = -4

Determine the values of a, b, and c for the quadratic equation:
 $y=4x^2–8x-3$  

• a = 4, b = -8, c = 3

• a = 4, b =-8, c =-3

• a = 4, b = 8, c = 3

• a = 4, b = 8, c = -3

Okay, so you probably feel good. Try this one. Determine the values of a, b, and c for the quadratic equation:
 $y=-2x^{ }+6x^2+10$  

• a = -2, b = 6, c = 10

• a = 10, b =-2, c = 6

• a = 6, b = -2, c = 10

• a = -2, b = 10, c = 6

Did I trick you?

• Yes. -____-

• Nah.

Now this one! Determine the values of a, b, and c for the quadratic equation:
 $y=8x^2-11$  

• a = 8, b = 0, c = -11

• a = 8,  b = -11 

• a = -11, b = 8

• a = 0, b = 8, c = 11

Okay, you got it! Now let's look at the formula for find the Axis of Symmetry. It's  $x=-\frac{b}{2a}$  (Write this down.) 

• Written!

• Got it!

What's the axis of symmetry of y = 3x² - 6x + 4

• x=1
• x=-6
• x=2
• x=-1

Tags

CCSS.HSA.REI.B.4