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3.2 – Solving Systems Algebraically. The goal of substitution is to put on equation into the other so there is only one variable to solve for. Substitution. Solve 1 of the equations for 1 of its variables Substitute the expression from Step 1 into the other equation and solve.
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The goal of substitution is to put on equation into the other so there is only one variable to solve for. Substitution
Solve 1 of the equations for 1 of its variables • Substitute the expression from Step 1 into the other equation and solve. • Substitute the value from Step 2 into an equation and solve for the remaining variable. Steps for Substitution
Example: Solve the linear system. 3x – y = 13 2x + 2y = -10
-x + 3y = 1 4x + 6y = 10
The goal with linear combination is to get one variable to cancel. • Then you will only have 1 equation with 1 unknown and you can solve for it. Linear Combination
What would you have to add to the following terms for their sum to be zero? • 3x • -2y • -x • 10y Think Opposite!
2 terms are given below. Find what you could multiply one (or two) term(s) by so that the sum of the two terms is zero. • 3x, x • -4y, 2y • 5x, 3x Think Opposite!
Make sure all like terms are lined up. • Multiply one or both equations by a constant so 1 variable will cancel when the 2 equations are added. • Add the two equations together and solve. • Substitute answer into an original equation to find the other variable. Steps to Solve by Linear Combination
1. 2x – 6y = 19 -3x + 2y = 10 Solve the following linear systems.
2. 3x + 2y = 10 5x - 7y = -4
3. 6x – 4y = 14 -3x + 2y = 7
4. 9x – 3y = 15 -3x + y = -5
Suppose you are going on vacation and leaving your dog in a kennel. The Bowowery charges $25 per day, which includes a one-time grooming treatment. The Poochpad charges $20 per day and a one-time fee of $30 for grooming. • Write a system of equations to represent the cost, c, for d days that your dog will stay at the kennel. • Find the number of days for which the costs are the same. • If your vacation is a week long, which kennel should you choose? Explain
You and your business partner are mailing advertising flyers to your customers. You address 6 flyers each minute and have already done 80. Your partner addresses 4 flyers each minute and has already done 100. Write a system of equations and find when you will have addressed the same number of flyers.