SOLUTION: The line y=2x+c is a tangent to the curve y=2x^2-6x+20.find the value of c

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Question 1159638: The line y=2x+c is a tangent to the curve y=2x^2-6x+20.find the value of c
Answer by math_helper(2461)   (Show Source): You can put this solution on YOUR website!


f'(x) =
For the tangent to just touch f(x), we need to find where f(x) has slope equal to 2:
4x-6 = 2 <<< remember, the ENTIRE LHS is the slope of f(x)
x = 2

At x=2: f(2) =
So the tangent line just meets f(x) at x=2, hence it has value 16 there:
2x + c = 2(2) + c = 16 ==> c = 12

Ans: and the tangent line is y=2x+12, and the point of tangency is (2,16).

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