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Find Equation of a Tangent Line?
y = x^2 - 2x, it's a tangent line with a slope of 2.
The answer should be y = 2x - 4
Is the solution to simply take the derivative which gives me:
dy/dx = 2x-2
Which I then put in standard y = mx + b form?
Which in turn would give me y = 2(x -2)
Which gives me the y = 2x - 4 answer in my book?
2 Answers
- ?Lv 58 years agoFavorite Answer
dy/dx = 2x - 2, slope is 2 so x=2. x=2 gives a y-value of 2^2 - 2(2) = 0, so a point on the tangent line is (2,0). This give a point-slope form of y-0 = 2(x-2), or y = 2(x-2). So you don't even need to put into y = mx + b, though if you prefer to do that there's nothing wrong with it.
- jacob sLv 78 years ago
dy/dx = 2x-2
dy/dx=m
2x-2=2
x=2
y = x^2 - 2x, when x=2 y=0
y=0
(2,0)
y-0=2(x-2)
y=2x-4