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Today in Precalculus. Go over homework Notes: Hyperbolas Completing the square Eccentricity Homework. Hyperbolas. Prove that the graph of 9x 2 – 4y 2 – 18x + 8y + 41 = 0 is an hyperbola. Find the center, vertices and foci. Then graph the hyperbola by hand.
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Today in Precalculus • Go over homework • Notes: Hyperbolas Completing the square Eccentricity • Homework
Hyperbolas Prove that the graph of 9x2 – 4y2 – 18x + 8y + 41 = 0 is an hyperbola. Find the center, vertices and foci. Then graph the hyperbola by hand. 9x2 – 18x – 4y2 + 8y = -41 9(x2 – 2x) – 4(y2 – 2y) = -41 9(x2 – 2x + 1) – 4(y2 – 2y + 1) = -41 + 9 - 4 9(x – 1)2 – 4(y – 1)2 = -36
Center: (1, 1) a = ±3 Vertices: (1, -2), (1, 4) c2 = 9 +4 = 13 c = ±3.6 Foci: (1, -2.6), (1,4.6 ) Pts on conjugate axis b = ±2 (-1,1), (3,1)
Example 2 Prove that the graph of 9y2 – 25x2 + 72y – 100x +269 = 0 is an hyperbola. Find the center, vertices and foci. Then graph the hyperbola by hand. 9y2 + 72y – 25x2 – 100x = -269 9(y2 + 8y) – 25(x2 + 4x) = - 269 9(y2 + 8y + 16) – 25(x2 + 4x + 4) = -269 +144 -100 9(y + 4)2 – 25(x + 2)2 = -225
Center: (-2, -4) a = ± 3 Vertices: (-5, -4), (1, -4) c2 = 9 + 25 =34 c = ±5.8 Foci: (-7.8, -4), (3.8, -4) Pts on conjugate axis b = ±5 (-2, -9), (-2, 1)
Eccentricity Where a is the semitranvserse axis and b is the semiconjugate axis. Example a: Example b:
Homework Page 664: 47-50 Ellipse and Hyperbola Quiz: Tuesday, February 26