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Mr. Sims Algebra 1 Solve with the substitution method. 1. Sect. 7.4 B Review of System of Equations 2x + y = 5 x–y=1 x=y+1 +y +y get one equation to read x = or y = 2(y + 1) + y = 5 2y + 2 + y = 5 3y + 2 = 5 distributive property combine like terms -2 -2 3y = 3 y=1 x=y+1 x=1+1 x=2 substitute into most efficient equation to solve for x Mr. Sims Solve with the addition method. 2. 3 2x – y = 3 4x + 3y = 21 multiply to cancel out variable when added 6x – 3y = 9 4x + 3y = 21 10x = 30 x=3 4x + 3y = 21 substitute into any equation with x and y 4(3) + 3y = 21 12 + 3y = 21 -12 -12 3y = 9 y=3 Mr. Sims Solve with the substitution method. 3. x – 2y = 4 x = 2y + 4 +2y +2y 6x + 2y = 10 get one equation to read x = or y = 6(2y + 4) + 2y = 10 12y + 24 + 2y = 10 14y + 24 = 10 -24 distributive property combine like terms -24 14y = -14 y = -1 x = 2y + 4 x = 2(-1) + 4 x = -2 + 4 x=2 substitute into most efficient equation to solve for x Mr. Sims Solve with the addition method. 4. 2 3x + 6y = 8 -6x + 3y = 2 multiply to cancel out variable when added 6x + 12y = 16 -6x + 3y = 2 15y = 18 4 3x 5 4 x 15 18 y 15 6 y 5 3x + 6y = 8 6 3x 6 8 5 36 3x 8 5 -36/5 substitute into any equation with x and y -36/5 Mr. Sims Solve with the substitution method. 5. x+y=0 -y x = -y -y 3x + 2y = 1 get one equation to read x = or y = 3(-y) + 2y = 1 -3y + 2y = 1 -y = 1 y = -1 x = -y x = -(-1) x=1 substitute into most efficient equation to solve for x Mr. Sims Solve with the addition method. 6. -3 2x – 3y = -7 2 3x + y = -5 -6x + 9y = 21 6x + 2y = -10 multiply to cancel out variable when added 11y = 11 y=1 3x + y = -5 3x + 1 = -5 substitute into any equation with x and y -1 -1 3x = -6 x = -2 Mr. Sims Algebra 1 Sect. 7.4 B Assignment Use the substitution method to solve the system. 1.) x + y = 2 -3x + 4y = 15 2.) x – y = -8 7x + 5y = 16 3.) x + 5y = 17 -4x + 3y = 24 Use the addition method to solve the system. 4.) 6x + y = -39 3x + 2y = -15 5.) 2x + 5y = 11 4x + 3y = 1 6.) 3x – 3y = -6 -5x + 6y = 12 Mr. Sims Any rebroadcast, reproduction, or other use of the pictures and materials from this site and presentations, without the express written consent of Mr. Sims, is prohibited. © Mr. Sims. All rights reserved. Mr. Sims