1. ## tangent line prob

At what point on the graph of y= 1/2x^2 is the tangent line parallel to the line 2x-4x=3?

I took the derivative of the first equation, and set it equal to the slope of the second and got that x was equal to 1/2. Then I plugged that back into the first equation to get that the y coordinate would be 1/8. However, the answer states that the y coordinate is -1/2. the only way to get that is to plug x=1/2 into the second equation. why do you use the second equation to find the point on the graph of the first? Thanks!

2. Originally Posted by abcocoa
At what point on the graph of y= 1/2x^2 is the tangent line parallel to the line 2x-4x=3?

I took the derivative of the first equation, and set it equal to the slope of the second and got that x was equal to 1/2. Then I plugged that back into the first equation to get that the y coordinate would be 1/8. However, the answer states that the y coordinate is -1/2. the only way to get that is to plug x=1/2 into the second equation. why do you use the second equation to find the point on the graph of the first? Thanks!
Hello,

first: There must be a typo in the equation of the line. I assume that you mean: 2x - 4y = 3.
Your results are correct so far.

Maybe you misread the problem? Howexactly is the text of the problem?

EB

3. ## nevermind

the answer in the back of the book was incorrect, so now i know how to do the prob. Thanks anyway.