5-Minute Check 1 Use elimination using addition to find the solution Bell Ringer 3-17 (4 minutes ) 1. In order to use elimination with addition, what do you need to have? (15 sec) 2. How is substitution used when doing the elimination method? (45 sec.) 3. p (2.5 min.) 4. Chapter 6 packet #15 (30 sec.) 5. HW Real-Life Packet #3 (4 min)
Elimination using Addition – Must have opposite coefficients – add the 2 equations together. Elimination using Subtraction – Must have the same coefficient. –Subtract the bottom equation from the top by changing all the signs in the bottom equation, then adding. –Then, add the 2 equations together. Elimination
HW Review – 5 min Chapter 6 Packet Do Skills Packet
Midterm Writing Practice
HW Real Life Packet 4, 8
Example 1 Multiply Both Equations to Eliminate a Variable Use elimination to solve the system of equations. 2x + y = 23 3x + 2y = 37 Multiply the first equation by 3 and the second equation by -2 to eliminate x. Distribute, then add the equations. 3(2x + y = 23) -2(3x + 2y = 37) – 1y = -5 Add the equations. -1 = -1 6x + 3y=69Multiply by 3. (+) -6x - 4y= -74Multiply by -2 Divide each side by –1. y=5Simplify.
Example 1 Multiply Both Equations to Eliminate a Variable Now substitute 5 for y in either original equation to find the value of y. Answer: The solution is (9, 5). 2x + y=23First equation 2x + 5 =23y = 5 2x + 5 – 5=23 – 5Subtract 18 from each side. 2x=18Simplify. x = 9Divide by 2 on each side
Example 2 Cell Phones: Cellular One offers a cell phone plan which the cost is determined by how many minutes and texts used. Within a monthly billing cycle, for every minute used, they charge $0.50 and for every text they charge $0.10. The customer pays $45 with Cellular One. Tee-Mobile’s cell phone plan only charges $0.30 for every minute used and $0.30 per text BUT charges a flat $5.00 usage fee per month. This customer pays $68.00 for their plan. a. Write a system of equations to represent this situation. Define your variables. American Cellular’s charges: Tee Mobile’s charges: b. What is the solution to the system in this problem? c. What does the solution represent?