Finding Your Way Around Quadratic Equations
Form Equation Example
Factored f(x) = a(x – s)(x – r) f(x) = 2(x – 3)(x + 5)
Equivalent
Standard f(x) = ax2 + bx + c f(x) = 2x2 + 4x – 30 Equations
Vertex f(x) = a(x – h)2 + k f(x) = 2(x + 1)2 – 32
Change
Given Key Points Action Example Method
to…
x-intercepts/ Take s and r
x-intercepts = (3,0)
solutions/ from the Expand:
and (-5,0) Standard f(x) = 2(x – 3)(x + 5)
roots equation
Form f(x) = 2(x2 + 2x -15)
f(0) = 2(0 – 3)(0 + 5) f(x) = 2x2 + 4x - 30
y-intercept Find f(0)
f(0) = -30
Factored Form
f(x) = 2(x – 3)(x + 5) AOS
Find vertex and sub for
Find AOS and x = (s + r)/2
h and k equation. Keep
sub into = (3 – 5)/2 Vertex
vertex a-value:
original = -1 Form
equation f(-1) = -32
f(x) = 2(x + 1)2 – 32
vertex = (-1, -32)
x-intercepts/ Factor or use ac/product = -15
solutions/ quadratic b/sum = 2 Factor:
roots formula f(x) = 2(x – 3)(x + 5) Factored ac/product = -15
Form b/sum = 2
“c” is the y- f(x) = 2(x – 3)(x + 5)
Standard Form y-intercept (0, c) = (0, -30)
intercept
f(x) = 2x2 + 4x - 30
Use x = -b/2a Find vertex and sub for
x = -4/[(2)(2)]
to find vertex h and k equation. Keep
x = -1 Vertex
vertex and sub into a-value:
f(-1) = -32 Form
original
vertex = (-1, -32)
equation f(x) = 2(x + 1)2 – 32
0 = 2(x + 1)2 – 32
x-intercepts/ 32 = 2(x + 1)2
Set equation Find roots and sub into
solutions/ 16 = (x + 1)2
equal to zero factored form. Keep
roots ±4 = x + 1 Factored
a-value:
x = 3 and -5 Form
Vertex Form
f(x) = 2(x – 3)(x + 5)
f(x) = 2(x + 1)2 – 32 f(0) = 2(0 + 1)2 – 32
y-intercept Find f(0)
f(0) = -30
From the Expand:
Standard
vertex equation vertex = (-1, -32) f(x) = 2(x+1)(x+1) – 32
Form
vertex = (h, k) f(x) = 2x2 + 4x - 30