MA 153
Lesson 26 Outline
Review from last lesson:
Parabolas:
1.
Standard Equation :
2
(
)
y
a x
h
k
=
−
+
Vertex:
( ,
)
h k
2.
Quadratic form:
2
y
ax
bx
c
=
+
+
Vertex can be found one of two ways:
1)
The
x
coordinate of the vertex is
2
b
x
a
= −
.
Substitute the
x
coordinate (once
known) into the equation to find the
y
coordinate.
OR
2)
Find the
x
intercepts (by factoring).
The
x
coordinate of the vertex is always in the
middle (the midpoint) of the
x
intercepts or
1
2
2
x
x
x
+
=
.
Again, substitute the
x

coordinate (once known) into the equation to find the
y
coordinate
For both forms:
“a” is the same number and tells you whether the parabola opens up or down.
If
, then the parabola opens up.
0
a
>
If
, then the parabola opens down.
0
a
<
The minimum/maximum value = the
y
coordinate of the vertex.
Answering of homework questions over lesson 24.
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