Transcript Finding a Quadratic Equation with the x

Finding a Quadratic Equation with the
x-intercepts and Another Point
Finding a Quadratic Equation with the
x-intercepts and Another Point
Find a rule for the quadratic table below.
x
y
-2
-15
-1
0
Since we
know the xintercepts
0
1
2
9
12
9
Sketch: Plot all the points Substitute into Factored Form:
The “a” is the GCF
(-1,0)
(3,0)
Use symmetry
to find any
missing xintercepts
Equation:
y  a  x  r1  x  r2 
Plug in the x-intercepts
y  a  x  1 x  3
Plug in another point
9

a
0

1
0

3



Solve
for a 9  3a
a  3
y  3  x  1 x  4
Finding a Quadratic Equation with the
x-intercepts and Another Point
Find a rule for the quadratic table below.
x
Y
There may
be a GCF
(adjustment
value)
-7
-6
-5
-4
-3
20
0
-10 -10 0
Substitute into Factored Form:
y  a  x  r1  x  r2 
Plug in the x-intercepts
y  a  x  6 x  3
Plug in another point
Since we
know the xintercepts
We need to solve
for “a” but there
are 3 variables

10

a

5

6

5

3



Solve
10  2a
for a
a 5
Equation:
y  5  x  6 x  3