1. Jan 10, 2008

### keltix

1. The problem statement, all variables and given/known data
definite integrals (1 + 3x) dx from (-1,5)

3. The attempt at a solution
i keep getting 6+54 but it should be 6+36

i think i might be using the wrong property

or multiplying wrong: 3[(6/n)i](6/n)

2. Jan 10, 2008

### mda

What do you get for the indefinite integral?

3. Jan 10, 2008

### J.D.

If it helps, remember that
$$\int^{b}_{a} x^n dx = { \left[ \frac{x^{n+1}}{n} \right] }^b_a$$.
And as mda said, it would be helpful to know how your calculations look.

4. Jan 11, 2008

the indefinite integral is " X + $$\frac{3}{2}$$X$$^{2}$$ " and if you calculate it for 5 to -1 the answer must be 42

5. Jan 11, 2008

### PWhiting1

If you integrate the function (3x+1) then it becomes (1.5x^2+x) where 5 is the upper limit and -1 is the lower. Sub in x=5 first, then minus the answer for x=-1 and you should end up with 42. When x=5 you should get 42.5, and when x=-1 you should get 0.5. Make sure that when you square -1 the calculator makes it 1, and does not leave it as -1 as some do.