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R—05/28/09—HW #73: Pg 477:47,49,50; Pg 490:17,49-61odd; Pg 496:31-55 eoo; Pg 505:25-59 odd 50) V=22000(.875)^t; 14,738. F—05/29/09—HW #74: Pg 469: 19-24; Pg 477: 19-24; Pg 496: 33-57 eoo; Pg 505: 26-58 even 20) E 22) A 24) D 20) E 22) B 24) A
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R—05/28/09—HW #73: Pg 477:47,49,50; Pg 490:17,49-61odd; Pg 496:31-55 eoo; Pg 505:25-59 odd 50) V=22000(.875)^t; 14,738
F—05/29/09—HW #74: Pg 469: 19-24; Pg 477: 19-24; Pg 496: 33-57 eoo; Pg 505: 26-58 even 20) E 22) A 24) D 20) E 22) B 24) A 26) -1\5 28) no sol 30) ln(1\6) 32) (ln 3)\5 34) ln 5\3 36) -.661 38) (ln5.5)\4 40) ln13.5 42) log255 44) 1\2 46) e^(15\8) 48) e^(5\2) 50) 15 52) .729 54) 256 56) no sol 58) no sol
An exponential function involves y = bx where the base b is positive and not equal to 1. An asymptote is a line the graph approaches. Usually represented by a dotted line An exponential growth function is when b > 1 An exponential decay function is when 0 < b < 1 Tell me if the following are growth or decay functions. Growth Growth Decay Decay
One to Review 1) Find key points 2) Add ‘h’ to the x-value 3) Multiply ‘a’ to the y-value 4) Add ‘k’ to the y-value h = 1 a = 2 k = -2 Other info to find: y – intercept: Asymptote: Domain: All real numbers Range: End behavior: x ∞; f(x) _____ x -∞; f(x) _____
A town of 5000grows at a rate of 10% per year. How many people are in town after 10 years? Find the info Write equation Answer question y = (1 + ) Calculator Plug – In 5000 * (1.1)^10 y = a(1 + r)t y final value a starting value r % increase, in decimal form (1 + r) Growth Factor t Time 12968 people (answers must make sense) 5000 5000 .1 .1 1.1 1.1 10 10
A car that costs 25,000 depreciates at a rate of 5% per year. A) What is the value of the car after 7 years? B) When is the car worth $20,000? Calculator – Windows and Intersect y = a(1 – r)t a r Decay factor t 25000 .05 .95 7
Let b and y be positive numbers, and b = 1. The LOGARITHM of y with base b is logby and is defined as logby = x if and only ifbx= y You read this log base b of y equals x.
Log Properties: g(x) = logbx is the inverse of f(x) = bx That means g(f(x)) = logbbx = x, and f(g(x)) = Try to make things match up with the base, and it’ll work out ok.
Finding inverses A) Simplify first 1) Switch x and y 2) Change forms 3) Simplify
Finding inverses A) Simplify first 1) Switch x and y 2) Change forms 3) Simplify
General Solving Rules • Methods of solving • Make bases of exponents the same • Notice when both sides have x as an exponent, and it looks like you can make bases the same. • Log both sides • Generally if you have a variable exponent on only one side. • Make the base of your log the same as the base of the exponent • Make terms inside logs equal • Both sides of the equation have logs with same bases • May involve condensing log expressions • Exponentiating both sides • One side has a log, one side doesn’t • May involve condensing log expressions • NEED TO DOUBLE CHECK!!!!
CAN’T HAVE NEGATIVE INSIDE OF LOGS! EXTRANEOUS SOLUTION. MUST ALWAYS DOUBLE CHECK!!!!!
Exponentiating both sides MUST ALWAYS DOUBLE CHECK!!!!!
R—05/28/09—HW #73: Pg 477:47,49,50; Pg 490:17,49-61odd; Pg 496:31-55 eoo; Pg 505:25-59 odd • F—05/29/09—HW #74: Pg 469: 19-24; Pg 477: 19-24; Pg 496: 33-57 eoo; Pg 505: 26-58 even