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To the parabola (x+2y)^2+2x-y-3=0 parallel to the line 4x+3y=2.
[From: ] [author: ] [Date: 11-08-13] [Hit: ]
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y = (-4/3) * x + (7/12)
y = (-4/3) * x + b
0 = (-4/3) * 1 + b
4/3 = b
y = (-4/3) * x + (4/3)
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Line 4x + 3y = 2 has slope = -4/3
So we need to find point on parabola where dy/dx = -4/3
We find dy/dx using implicit differentiation:
(x + 2y)² + 2x - y - 3 = 0
2(x+2y) (1 + 2 dy/dx) + 2 - dy/dx - 0 = 0
2(x+2y) + 4(x+2y) dy/dx + 2 - dy/dx = 0
4(x+2y) dy/dx - dy/dx = -2(x+2y) - 2
dydx (4x+8y-1) = -2(x+2y+1)
dy/dx = -2(x+2y+1) / (4x+8y-1)
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Now we let dy/dx = -4/3
-2(x+2y+1) / (4x+8y-1) = -4/3
2(x+2y+1) / (4x+8y-1) = 4/3
4(4x+8y-1) = 6(x+2y+1)
16x + 32y - 4 = 6x + 12y + 6
10x = 10 - 20y
x = 1 - 2y
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Now we substitute x with (1-2y) in equation of parabola, and solve for y:
(x + 2y)² + 2x - y - 3 = 0
(1-2y + 2y)² + 2(1-2y) - y - 3 = 0
(1)² + 2 - 4y - y - 3 = 0
-5y = 0
y = 0
x = 1-2y = 1
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Line tangent to parabola with slope = -4/3 passes through point (1, 0)
y = -4/3 (x - 1)
y = -4/3 x + 4/3
4x + 3y = 4
http://www.wolframalpha.com/input/?i=%28…
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