Answer it::: Very urgent..
Find the area bounded by the parabola y^2= 4x and the line y=2x-4. by both vertical and horizontal method. Its not equal, how??

Hello Japleen Kaur dear, really an head-ache for beginners with this.
As you draw the figure and just at it
If you take the technique of finding the area bounded by the line and the curve on the right side of y axis we have total needed area.
But if you want to get the same area using x axis then there comes a problem of having area above x axis (positive) and below x axis (negative).
So as you calculate without giving this consideration then area in the latter will be less than the initial one.
If you want to get the same answer as in the first case then you have to split into two and one above and the other below and then you have to add them. (- of - gives plus)
Hope you have got it. 
So by vertical strip we get it readily without any confusion