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Do Now 10/15/10 Take out HW from last night. Textbook p.179-181 #4-36 even Copy HW in your planner. Textbook p. 187 #4-30 even “Pop” Quiz sections 3.5-3.8 Tuesday

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Homework Textbook p.179-181 #4-36 even 4) 55% 6) 51 8) 21 10) 44% 12) 27 14) 176.3 16) 210 18) 137.5 20) p% should be multiplied by 95; p% = 20% 22) 85% 24) 33.8 26) 16% 28) 72% 30) Equation; multiply the base times the percent to find the part. 32) 5y 34) 200 laps 36) YearHikers who Started Hikers who Completed Percent Completion 2001238039516.6% 2002188037620% 2003175035220%

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Objective SWBAT rewrite equations and formulas

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Section 3.8, “Rewrite Equations and Formulas” Literal Equation- an equation where the coefficients and constants are replaced by letters. The equation 2x + 5 = 11 has the general form ax + b = c. ax + b = c.

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Solving a Literal Equation Subtract b from each side. Write original equation. Solve ax + b = c for x. STEP 1 SOLUTION Solve ax +b = c for x. Then use the solution to solve 2x + 5 = 11. x c – b a = ax + b = c ax = c – b Assume a 0. Divide each side by a. =

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The solution of 2x + 5 = 11 is 3. ANSWER Simplify. Substitute 2 for a, 5 for b, and 11 for c. Solution of literal equation. Use the solution to solve 2x + 5 = 11. STEP 2 11 – 5 2 = x = c – b a =3 Solving a Literal Equation

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Try It Out Subtract a from each side. Write original equation. Solve a – bx = c for x. STEP 1 SOLUTION 1. Solve a – bx = c for x. x a – ca – c b = a – bx = c – bx = c – a Assume b 0. Divide each side by – 1b. = Solve the literal equation for x. Then use the solution to solve the specific equation

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Try It Out The solution of 12 – 5x = –3 is 3. ANSWER Simplify. Substitute a for 12, –3 for c, and 5 for b. Solution of literal equation. Use the solution to solve 12 – 5x = –3. STEP 2 12 – (–3) 5 = x = a – c b =3

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Try It Out Subtract bx from each side. Write original equation. Solve a x = bx + c for x. STEP 1 SOLUTION 2. Solve a x = bx + c for x. c x a – ba – b = a x = bx + c a x – bx = c Assume a 0. Divide each = side by a – b.

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Try It Out The solution of 11x = 6x + 20. is 4. ANSWER Simplify. Solution of literal equation. Use the solution to solve 11x = 6x + 20. STEP 2 20 11 – 6 = x = c a – b =4 Substitute a for 11, 20 for c, and 6 for b.

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Rewriting Equations with Multiple Variables An equation or formula with 2 or more variables, such as 3x + 2y = 8 or A = ½bh, can be rewritten so that one variable is a function of the other variable(s). 3x + 2y = 8 This equation can be rewritten so that y is a function of x. A = ½bh This equation can be rewritten so that you can solve for h.

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Try It Out Divide each side by 2. Write original equation. Write 3x + 2y = 8 so that y is a function of x. Subtract 3x from each side. 3x + 2y = 8 2y2y = 8 – 3x 3 2 y=4 – x

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Try It Out Multiply each side by 2. Write original formula. SOLUTION Solve the formula for the height h. a. The area A of a triangle is given by the formula A = bh where b is the base and h is the height. 12 a. bh 1 2 A = 2A2A = Divide each side by b. 2A2A b h =

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Try It Out Substitute 64.4 for A and 14 for b. Write rewritten formula. Substitute 64.4 for A and 14 for b in the rewritten formula. = 2(64.4) 14 = 9.2 Simplify. ANSWERThe height of the triangle is 9.2 meters. h 2A2A b = Use the rewritten formula to find the height of the triangle shown, which has an area of 64.4 square meters. b.

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Rewrite the following formulas in terms for each variable. Rewrite the following formulas in terms for each variable. Temperature Temperature Distance Traveled Distance Traveled Profit Profit Simple Interest Simple Interest

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Temperature Temperature Distance Traveled Distance Traveled Profit Profit Simple Interest Simple Interest

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Challenge The surface area of a cone is given by the formula below. Solve for the length.

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