Wednesday, September 28, 2016

College Algebra, Chapter 8, Review Exercises, Section Review Exercises, Problem 42

Identify the type of curve which is represented by the equation x2+4y2=4x+8
Find the foci and vertices(if any), and sketch the graph

x24x+4y2=8Subtract 4xx24x+4+4y2=8+4Complete the square; Add (42)2=4(x2)2+4y2=12Perfect square(x2)212+y23=1Divide by 12


The equation is an ellipse that has form (xh)2a2+(yk)2b2=1 with center at (h,k) and horizontal major axis.
Since, the denominator of x2 is bigger. The graph of the shifted ellipse is obtained by shifting the graph of x212+y23=1
by 2 units to the right. This gives us a2=12 and b2=3. So, a=23,b=3 and c=a2b2=123=3. Thus,
by applying transformatioms, we have

center (h,k)(2,0)vertices: major axis(a,0)(23,0)(23+2,0)=(23+2,0)(a,0)(23,0)(23+2,0)=(23+2,0)minor axis (0,b)(0,3)(0+2,3)=(2,3)(0,b)(0,3)(0+2,3)=(2,3)foci (c,0)(3,0)(3+2,0)=(5,0)(c,0)(3,0)(3+2,0)=(1,0)

Therefore, the graph is

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