# Evaluating integrals

1. May 13, 2013

### mathpat

1. The problem statement, all variables and given/known data

Given
7 f(x) dx= 8
0

7 f(x) dx = −3
1

evaluate the following.

1 f(x) dx
0

2. Relevant equations
n/a

3. The attempt at a solution

I'm a little confused on how to approach this problem. Do i use the additive interval property of integrals?

2. May 13, 2013

### Staff: Mentor

Yes.

3. May 13, 2013

### mathpat

I ended up with 5. Is that correct?

Last edited: May 13, 2013
4. May 13, 2013

### Staff: Mentor

So 5 + (-3) = 8?

5. May 13, 2013

### UVW

To expand on what Mark44 is saying, remember that these integrals represent areas under your curve, f(x). If you know how much area is under the curve between x = 0 and x = 7 and also know how much area is under the curve between x = 1 and x = 7, can you intuitively decide how to find the area between x = 0 and x = 1?

6. May 13, 2013

### mathpat

Yea I understand but when I use the formula i keep getting 5. I don't see where I'm going wrong.

7. May 13, 2013

### Infrared

$\int_0^7 f(x) dx = \int_0^1 f(x) dx + \int_1^7 f(x) dx$. What happens when you plug in what you know?

8. May 13, 2013

### mathpat

I calculated 11 using that formula.

9. May 13, 2013

### Infrared

Good, that's right.

10. May 13, 2013

### mathpat

Thanks

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