Systems
description
Transcript of Systems
You can open your book to page 417 to refresh your memory as you start your warm-up. The information presented in this lesson will
be included in sections 9-2, 9-4, and 9-5.
Please take 5 minutes to work on the following problems…
1. x+y= 154x+3y= 38
2. 6c+7d= -156c-2d= 12
3. 3a+4b= 25a+9b= 1
1) Solve one equation for one of the variables2) Substitute this expression in the other
equation and solve for the other variable3) Substitute this value in the equation in step
1 and solve4) Check the values in both equations
Example 1: 2x-3y=4x+4y= -9
1.) 2x-3y=4x= -9-4y
2.) 2(-9-4y)-3y=4y= -2
3.) x+4(-2)= -9x= -1
4.) 2(-1)-3(-2)=4 4=4 yes(-1)+4(-2)= -9 -9= -9
yesAnswer (-1,-2)
Use the 4 step process…
Solve one equation
Substitute and solve in other equation
Substitute this value in the equation in step 1 and solve
Check
Example 2: 2x-8y=6x-4y=8
1.) 2x-8y=6x=4y+8
2.) 2(4y+8)-8y=616=6 no
3.) No solution; special case where the variables cancel each other out and the 4 step process does not work.
Use the 4 step process…
Solve one equation
Substitute and solve in other equation
Substitute this value in the equation in step 1 and solve
Check
1. Add or subtract the equation to eliminate one variable
2. Solve the resulting equation for the other variable
3. Substitute in either original equation to find the value of the first variable
4. Check in both equations
Example 1: 2c+3d=0 + 5c-3d=21
1.) 7c=21 7 7
2.) c=3
3.) 2(3)+3d=06+3d=0d= -2
4.) 2(3)+3(-2)=00=0 yes
5(3)-3(-2)=21 21=21 yes
Answer (3,-2)
Add or subtract the equation to eliminate one
variable
Solve the resulting equation for the other variable
Substitute in either original equation to find the value of the first variable
Check in both equations
5 Step Addition and Subtraction Process Using Multiplication
Multiply one or both the equations so the absolute value of the coefficients of one of the variables are equal
Add or subtract the equation to eliminate one variable
Solve the resulting equation for the other variable
Substitute in either original equation to find the value of the first variable
Check in both equations
• Example 2: 4x+5t=225x-t= 13
1.) 4x+5t=22
(5)5x-t= 13(5)
2.) 4x+5t=22
+ 25x-5t=653.) 29x=87
29 29 x=3
4.) 5(3)-t=13t=2
5.) 4(3)+5(2)=22 22=22 yes
5(3)-2=13 13=13 yes
Answer (2,3)
• Example 3: 6n+8c-4=09n+10c-7=0
1.) (3/2)6n+8c-4=0(3/2)
9n+10c-7=0
2.) 9n+12c-6=0-(9n+10c-7=0)
2c= -13.) 2 2 c= -1/24.) 6n+8(-1/2)-4=0
n= 4/35.) 6(4/3)+8(-1/2)-
4=0 0=0 yes
9(4/3)+10(-1/2)-7=0 0=0 yes
Answer (-1/2, 4/3)
5 Step Addition and Subtraction Process Using Multiplication
Multiply one or both the equations so the absolute value of the coefficients of one of the variables are equal
Add or subtract the equation to eliminate one variable
Solve the resulting equation for the other variable
Substitute in either original equation to find the value of the first variable
Check in both equations
Please take 5 minutes to complete your assessment…
1.y/2= 2-x6x+3y= 12
2.5x-y= 123x+y= 4
3.4x-5y= 233x+10y= 31
-Remember…-To solve any system you must find the
value of one variable-After that you substitute that answer in
one equation to find the other variable-Finally you check your answers
(Important to have on foldable)