If the normal to the curve y=xlnxy=xlnx is parrallel to the straight line 2x-2y+3=02x2y+3=0 ,then the normal equation is...... a.x-y=3e^-2xy=3e2 b.x-y=6e^-2xy=6e2 c.x-y=3e^2xy=3e2 ?

1 Answer
May 10, 2018

Option A is correct .

Explanation:

The line can be rewritten a

2x + 3 = 2y2x+3=2y

x + 3/2 = yx+32=y

So the slope of the line (as well as the normal line) will be 11. This means the slope of the tangent will be -11, so we have to set the derivative to -11.

y' = lnx + x(1/x) = lnx + 1

We have:

-1= lnx + 1 -> lnx = -2 -> x = e^-2

The corresponding value of y is y = e^-2ln(e^-2) = -2e^-2

We now can see that the normal has equation

y - (-2e^-2) = x - e^-2

y = x - e^-2 - 2e^-2

y = x - 3e^-2

Or

x - y = 3e^-2

Which is option A.

Hopefully this helps!