Enter the equation describing the first of your curves into your scientific calculator. Press the "integrate" button to produce the integral of the function. For example, if you enter x^2+1, the result will be 2x. Make a note of the answer.
Enter the equation describing the second of your curves into your scientific calculator. Press the "integrate" button to produce the integral of the function. Make a note of the answer.
Type out the first equation you found in step 1 in your scientific calculator, but instead of entering the variable term, enter the first limit. The limits are the portions of the two curves you want to find the areas between. The first limit is the smaller of the two. An example of the limits you might want to find for the areas between two curves are the limits from x = 0 (the origin) to x = 20; in this example, x = 0 is the first limit and x = 20 is the second limit. The variable term is whatever letter you are using to symbolize the variables in the equations defining your curves. For example, if your equation is y = 2x, the variable term would be x. Make a note of the value produced as a result of entering the first limit into the variable term of the first equation.
Type out the first equation your found in step 1 in your scientific calculator, but this time, instead of entering the variable term, enter the second limit. Make a note of this value. Subtract the value found in step 3 from the value found in step 4. This value represents the area under the first curve. Make a note of this value.
Type out the equation you found in step 2 in your scientific calculator, but instead of entering the variable term, enter the first limit. Make a note of this value.
Type out the equation you found in step 2 in your scientific calculator, but instead of entering the variable term, enter the second limit. Make a note of this value.
Subtract the value from step 5 from the value found in step 6, using your scientific calculator. This value is the area under the second curve between the limits
Subtract the value found in step 4 from the value found in step 7. This represents the area of the difference between the two curves and the given limits.