
<p> Lesson 12 Section 2.3</p><p>Compare the graphs of the lines below. A B C y = 2x y = 2x + 3 y = 2x - 4 x y x y x y 0 0 0 3 0 -4 -1 -2 -1 1 -1 -6 2 4 2 7 2 0 -3 -6 -3 -3 -3 10 y y</p><p> x</p><p>How does each point of graph B compare with graph A (directly below)?</p><p>How does each point of graph C compare with graph A (directly above)?</p><p>If the equations of B and C are considered to be in the form y = mx + b, the point (0, b) represents the y-intercept. The value of m represents the 'slant' of the line, called the slope. 1st way to find slope</p><p> vertical change rise difference of y's y y y y slope = m = 2 1 or 1 2 2nd way horizontal change run difference of x's x2 x1 x1 x2 SLOPE FORMULA: to find y y slope m 2 1 x2 x1 The vertical change (rise) can be compared to the horizontal change (run) by ‘counting’ on a graph. rd Find the slope of each line described. 3 way to find slope</p><p>(4,0) (-1,-1) x</p><p>1)</p><p> y</p><p>2) 4x 5y 20</p><p>3) points: (-2, -8) and (-3, 1)</p><p>2 1 4) x y 1 3 4</p><p>5) points: (3, 0) and (-4, -10)</p><p>(-2,2)</p><p> x (1,-2)</p><p>6)</p><p> y Slope-Intercept Form: The form y = mx + b is called the slope-intercept form where m is the slope and (0, b) is the y-intercept. The form f (x) mx b is slope-intercept form of a linear function. 3 2 7) Write a linear function for a line with slope and y-intercept 0, . 2 3 </p><p>8) Find the slope and y-intercept. 3x 2y 12</p><p>You can graph a line using the slope and y-intercept. Begin on the y-axis at the y-intercept. Count ‘up or down’ corresponding to rise, then ‘left or right’ corresponding to run to find another point. Draw the line. 5 9) Use the slope and y-intercept to graph the line. f (x) x 2 2</p><p> x</p><p> y 5 10) g(x) x 3 3</p><p> x</p><p> y 11) Determine the slope and y-intercept, then graph. 4x 2y 8</p><p> x</p><p> y</p><p>12) Graph h(x) 2 APPLICATIONS 1) Year % of U.S. homes with multiple computers 1997 10 1998 13.6 1999 17.2 2000 20.8 2001 24.4 Notice: Each year, the percent of U.S. homes with multiple computers grew by 3.6%. This is called the rate of change and is equal to the slope, if a graph was made with the x-axis representing years and y-axis representing percent. 2) The graph below represent the value of a computer model (in hundreds of dollars) for a number of years after it is used.</p><p>30 s</p><p> r 24 r a l e l t o u d p</p><p> f 18 m o o s c</p><p> d f e o r</p><p> d e n u 12 l u a h v n i 6</p><p>0</p><p>1 2 3 4 years since used a) Find the rate of change.</p><p> b) Find an function in slope-intercept form where V(t) is value and t is number of years in use.</p><p> c) Use this function to find the value at 2 years.</p><p> d) What is the domain of this function? 3) What do m and b represent in this function? After a child gets a 'buzz' haircut, the length 1 of his hair L(t) in inches is given by L(t) t 1, where t is the number of months after the 2 haircut.</p><p>4) Acme shirt company uses V (t) 2000t 15000 to determine the salvage value of a color separator t years after it is put into use. a) What do -2000 and 15000 represent?</p><p> b) How long does it take for the machine to depreciate entirely?</p><p> c) What is the domain?</p><p>4) The function f (t) 0.5t 7 can be used to estimate the cash receipts, in billions of dollars, from farm marketing of cotton t years after 1995. a) What are the cash receipts in 1999?</p><p> b) In what year was the cash receipts $3.5 billion?</p>
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