lesson 9.7 solve systems with quadratic equations essential question: how do you solve systems that...
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Lesson 9.7 Solve Systems with Quadratic EquationsEssential Question: How do you solve systems that include a quadratic equation?
CC.9.12.A.REI.4bSolve quadratic equations by inspection, by taking square roots, completing thesquare, the quadraticformula and factoring, as appropriate to theinitial form of theequation. Recognizewhen the quadratic formula gives complexsolutions.
Warm-up:
1. Solve the linear system using substitution. y = 3 – 2x y = x + 9
2. Solve the linear system using elimination. x – y = 10 4x + y = -15
4-15-13
2 8
10
x y
x y
Systems of Linear EquationsWe had 3 methods to solve them.
Method 1 - Graphing
Solve for y.
2 8y x
10y x (6, – 4)
Systems of Linear Equations
Method 2 - Substitution
2 8
10
x y
x y
2 8y x
10x y 10x 2 8x
2 8 10x x 3 18x
6x 6
2 8y x 2( ) 8y 12 8y 4y
(6, – 4)
Systems of Linear Equations
Method 3 - Elimination
2 8
10
x y
x y
2 8
10
x y
x y
3 18x
6x 6
10x y ( ) 10y 4y 4y
(6, – 4) All 3 methods
giving us the
same answer
(6,–4).
Solving Systems of Linear and Quadratic Equations
Substitution Method
• Step 1: Solve one of the equations for one of its variables.
• Step 2: Substitute the expression from step 1 into the other equation and solve for the other variable.
• Step 3: Substitute the value from step 2 into one of the original equations and solve.
Example 1 Use Substitution Method
• Solve the system:263
232
xxy
xy
Systems with One Linear Equation and One Quadratic Equation
No solution One Solution Two Solutions
Solve the System AlgebraicallyUse Substitution
1
12
xy
xy
1 xy( ) 1x
Answer: (0,1) (1,2)
2 1x
02 xx
1 0x x 0 1 0x or x 0 1x or x
0x 20 1
1
y
y
(0, 1)
1x 21 1
2
y
y
(1, 2)
Solve the System AlgebraicallyUse Substitution
2 2y x 2( ) 2 2x x 22 x
Answer: (2,2)
2 2 2y x x 2x
(2, 2)
22
222
xy
xxy
20 4 4x x 0 2 2x x
0 2x 2x
2 2 2
4 2
2
y
y
y
Solve the System AlgebraicallyUse Substitution
6y x
22 6 26x x 2 2 12 36 26x x x
6
2622
yx
yx
22 12 10 0x x 2 6 5 0x x
5 1 0x x
5 1x or x
5x 5 6
1
1
y
y
y
1x 1 6
5
5
y
y
y
(5, –1)
(1, – 5)
Answer: (5, –1) (1, – 5)
Solve the System AlgebraicallyUse Substitution
3
4y x
22 3
254
x x
2 2925
16x x
2 216 9 400x x 225 400x 2 16x
4x
4x 4 3 4
4 12
3
y
y
y
4x 4 3 4
4 12
3
y
y
y
(4, 3)
(– 4, – 3)
Answer: (4, 3) (–4, – 3)
xy
yx
34
2522
Now let’s look at the Graphs of these Systems!
Classify each equation as linear/quadratic.
What does the graph of each look like?Line
Parabola
Linear
Quadratic
What is the solution to the system?
Point of Intersection (-2, 0)
Point of Intersection (1, -3 )
1
12
xy
xy
Answer: (0,1) (1,2)
22
222
xy
xxy
Answer: (2,2)
Now use your calculator to check it graphically.
We have solved the following algebraically
Classwork/Homework
•9.7 Exercises •Pages 625 •2- 20 even•Quiz on Quadratic formula on Tuesday!