Problem 21 - Introductory Algebra for College Students

Question

Find each sum without the use of a number line. $$-9+4$$

Step-by-Step Solution

Answer

-5

Step 1: Identify the Numbers

The numbers mentioned in the problem are -9 and 4. The number -9 is a negative number while 4 is a positive number.

Step 2: Apply Rule of Adding Positive Number to Negative Number

When adding a positive number to a negative number, one must subtract the positive number from the absolute value of the negative number. So, start by converting -9 to its absolute value, which is 9. Then subtract 4 from 9.

Step 3: Perform the Operation

Subtracting 4 from 9 results in 5. However, remember that the original number was negative. Therefore, when adding -9 and 4, the result should also be negative.

Step 4: Conclusion

Therefore, -9 + 4 = -5