Chapter 8 Variation
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Relations between Changing Quantities In a fixed hour, we go further if we ride faster.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation It takes less time to complete a 100 m race when we run faster. Relations between Changing Quantities
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Lighting up more bulbs can make the room brighter. Relations between Changing Quantities
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation We pay more if we travel a longer distance. Relations between Changing Quantities
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation With the same amount of money, we get less food if the price is higher. Relations between Changing Quantities
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation We experience certain relations among changing quantities in our daily life. Speed Distance Speed Time Number of candles Brightness Distance Fares Price Quantity bought Relations between Changing Quantities
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Direct Variation (I) x y and x y The meaning of y varies directly as x: The value of keeps unchanged Symbolically, y x In the form of equation, y kx where k is a non-zero constant.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation The graph of equation y kx is a straight line passing through the origin. Direct Variation (I)
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Direct Variation (II) x 2 y and x 2 y The meaning of y varies directly as x 2 : The value of keeps unchanged Symbolically, y x 2 In the form of equation, y kx 2 where k is a non-zero constant.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Direct Variation (II) The graph of equation y kx 2 is a curve.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation where u x 2 Direct Variation (II) The graph of equation y ku is a straight line passing through the origin.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Inverse Variation x y and x y The value of xy keeps unchanged The meaning of y varies inversely as x: Symbolically, In the form of equation, or xy k where k is a non-zero constant.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Inverse Variation The graph of equation is a curve.
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Inverse Variation The graph of equation y ku is a straight line passing through (but does not include) the origin. Graph of y against u u where
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Joint Variation If h is fixed, then y varies directly as r 2. If r is fixed, then y varies directly as h. Symbolically, y hr 2 In the form of equation, y khr 2 where k is a non-zero constant. The meaning of y varies jointly as h and r 2 :
2004 Chung Tai Educational Press © Chapter Examples Quit Chapter 8 Variation Partial Variation y is the sum of two parts. One part of y varies directly as h. Other part of y varies directly as b. In the form of equation, y k 1 h k 2 b where k 1 and k 2 are non-zero constants. The meaning of y partly varies directly as h and partly varies directly as b:
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