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- Systems of linear equations
- Elimination by addition
Practice set a
Solve each system by addition.
Sample set b
Solve the following systems using the addition method.
Solve
Step 1: The equations are already in the proper form,
Step 2: If we multiply equation (2) by —3, the coefficients of
will be opposites and become 0 upon addition, thus eliminating
.
Step 3: Add the equations.
Step 4: Solve the equation
Step 5: Substitute
into either of the original equations. We will use equation 2.
We now have
and
Step 6: Substitute
and
into both the original equations for a check.
Step 7: The solution is
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Solve
Step 1: Rewrite the system in the proper form.
Step 2: Since the coefficients of
already have opposite signs, we will eliminate
.
Multiply equation (1) by 5, the coefficient of
in equation 2.
Multiply equation (2) by 2, the coefficient of
in equation 1.
Step 3: Add the equations.
Step 4: Solve the equation
Step 5: Substitute
into either of the original equations. We will use equation 1.
We now have
and
Step 6: Substitution will show that these values check.
Step 7: The solution is
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Practice set b
Solve each of the following systems using the addition method.
Addition and parallel or coincident lines
When the lines of a system are parallel or coincident, the method of elimination produces results identical to that of the method of elimination by substitution.
Addition and parallel lines
If computations eliminate all variables and produce a contradiction, the two lines of the system are parallel and the system is called inconsistent.
Addition and coincident lines
If computations eliminate all variables and produce an identity, the two lines of the system are coincident and the system is called dependent.
Sample set c
Solve
Step 1: The equations are in the proper form.
Step 2: We can eliminate
by multiplying equation (1) by –2.
Step 3: Add the equations.
This is false and is therefore a contradiction. The lines of this system are parallel. This system is inconsistent.
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Solve
Step 1: The equations are in the proper form.
Step 2: We can eliminate
by multiplying equation (1) by –3 and equation (2) by 4.
Step 3: Add the equations.
This is true and is an identity. The lines of this system are coincident.
This system is dependent.
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Practice set c
Solve each of the following systems using the addition method.
Exercises
For the following problems, solve the systems using elimination by addition.
Exercises for review
Questions & Answers
If auger is pair are the roots of equation x2+5x-3=0
Wayne and Dennis like to ride the bike path from Riverside Park to the beach. Dennis’s speed is seven miles per hour faster than Wayne’s speed, so it takes Wayne 2 hours to ride to the beach while it takes Dennis 1.5 hours for the ride. Find the speed of both bikers.
from theory: distance [miles] = speed [mph] × time [hours]
info #1
speed_Dennis × 1.5 = speed_Wayne × 2
=> speed_Wayne = 0.75 × speed_Dennis (i)
info #2
speed_Dennis = speed_Wayne + 7 [mph] (ii)
use (i) in (ii) => [...]
speed_Dennis = 28 mph
speed_Wayne = 21 mph
George
Let W be Wayne's speed in miles per hour and D be Dennis's speed in miles per hour. We know that W + 7 = D and W * 2 = D * 1.5.
Substituting the first equation into the second:
W * 2 = (W + 7) * 1.5
W * 2 = W * 1.5 + 7 * 1.5
0.5 * W = 7 * 1.5
W = 7 * 3 or 21
W is 21
D = W + 7
D = 21 + 7
D = 28
Salma
Devon is 32 32 years older than his son, Milan. The sum of both their ages is 54 54. Using the variables d d and m m to represent the ages of Devon and Milan, respectively, write a system of equations to describe this situation. Enter the equations below, separated by a comma.
find product (-6m+6) ( 3m²+4m-3)
what is the solution
bill
how did you arrive at this answer?
bill
i really want to learn
Amira
I only got 42 the rest i don't know how to solve it. Please i need help from anyone to help me improve my solving mathematics please
Amira
Hw did u arrive to this answer.
Aphelele
-6m(3mA²+4m-3)+6(3mA²+4m-3)
=-18m²A²-24m²+18m+18mA²+24m-18
Rearrange like items
-18m²A²-24m²+42m+18A²-18
Salma
complete the table of valuesfor each given equatio then graph.
1.x+2y=3
given that (7x-5):(2+4x)=8:7find the value of x
Nandala
please why isn't that the 0is in ten thousand place
please why is it that the 0is in the place of ten thousand
Grace
Send the example to me here and let me see
Stephen
A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of one of the other legs. Find the lengths of the hypotenuse and the other leg
state in which quadrant or on which axis each of the following angles given measure. in standard position would lie 89°
I am eliacin, I need your help in maths
Rood
hmm can we speak here?
Amoon
however, may I ask you some questions about Algarba?
Amoon
what the last part of the problem mean?
Roger
The Jones family took a 15 mile canoe ride down the Indian River in three hours. After lunch, the return trip back up the river took five hours. Find the rate, in mph, of the canoe in still water and the rate of the current.
Shakir works at a computer store. His weekly pay will be either a fixed amount, $925, or $500 plus 12% of his total sales. How much should his total sales be for his variable pay option to exceed the fixed amount of $925.
I'm guessing, but it's somewhere around $4335.00 I think
Lewis
12% of sales will need to exceed 925 - 500, or 425 to exceed fixed amount option. What amount of sales does that equal? 425 ÷ (12÷100) = 3541.67. So the answer is sales greater than 3541.67.
Check:
Sales = 3542
Commission 12%=425.04
Pay = 500 + 425.04 = 925.04.
925.04 > 925.00
Munster
difference between rational and irrational numbers
When traveling to Great Britain, Bethany exchanged $602 US dollars into £515 British pounds. How many pounds did she receive for each US dollar?
how to reduced echelon form
Jazmine trained for 3 hours on Saturday. She ran 8 miles and then biked 24 miles. Her biking speed is 4 mph faster than her running speed. What is her running speed?
d=r×t
the equation would be 8/r+24/r+4=3
worked out
Sheirtina
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Source:
OpenStax, Elementary algebra. OpenStax CNX. May 08, 2009 Download for free at http://cnx.org/content/col10614/1.3
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