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The tangent to the curve y = x−3x^(-1) at (x, y) = (1,−2) meets the x-axis at (a,0) where a =?
I have been trying to figure out what exactly this questions means. I can find the derivative of the y, it's 1+3/x^2. However, I don't get what this question is asking me to solve for.
Thanks.
2 Answers
- MechEng2030Lv 710 years agoFavorite Answer
y = x - 3x^(-1)
dy/dx = 1 + 3/(x^2)
Slope of tangent to curve at (1, - 2) = 1 + 3 = 4
Eqn of tangent line:
y + 2 = 4(x - 1)
y = 4x - 6
Find the x-intercept:
4x - 6 = 0
x = 3/2
Therefore, a = 3/2
- 10 years ago
it means the line given by the tangent to the curve at (1,-2) intersects the x axis at a certain point (a,0)
so basically you have to find the equation of a line where the slope (m) is equal to y' at x= 1.
so... y = m*x +b
once you have m (just sub in x = 1 into the derivative of y (y')) you can set x and y to 1 and -2 in your y = mx+b equation and then solve for b.
Now that you have the equation of the line, check what x is equal to when you set y = 0;
this will give you the a value