# 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.

## Presentation on theme: "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."— Presentation transcript:

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

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%

Objective SWBAT rewrite equations and formulas

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.

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. =

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

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

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

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.

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.

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.

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

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 =

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.

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

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

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

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