# Math Help - Definite Integral of dx

1. ## Definite Integral of dx

$\int_{1}^{8}dx$

I was given this question, and I have no idea whether the answer for this would be 0, or 7?

Is there an invisible 1 in there, or is it integrating 0?

Thankyou.

2. Originally Posted by Eldar
Is there an invisible 1 in there, or is it integrating 0?
There is 1.

3. The graph of y= 1 is a horizontal straight line. The integral would be equal to the area below that straight line, from x= 1 to x= 7. That is, the area of a rectangle with length 8- 1= 7 and height 1.