evaluate meantally
3-15+4
-34-6+12
5(-9-4)
5-3(-4)
1/2(-26)
14-21/-7
-5^2
(-5)^2
-8
-28
-65
-13
1
25
To evaluate these expressions mentally, you can follow the order of operations, which is commonly remembered using the acronym PEMDAS (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction).
1. 3 - 15 + 4:
The first step is to perform the subtraction: 3 - 15 = -12.
Then, add the result with 4: -12 + 4 = -8.
2. -34 - 6 + 12:
First, perform the subtraction: -34 - 6 = -40.
Then, add the result with 12: -40 + 12 = -28.
3. 5(-9 - 4):
Start by performing the operation inside the parentheses: -9 - 4 = -13.
Next, multiply the result by 5: 5 * -13 = -65.
4. 5 - 3(-4):
Multiply the number inside the parentheses by the coefficient: 3 * -4 = -12.
Substitute the result back into the expression: 5 - (-12).
To simplify, remember that -(-12) is equivalent to +12.
So, the expression becomes 5 + 12 = 17.
5. 1/2(-26):
Multiply the fraction by the number inside the parentheses: 1/2 * -26 = -13.
6. 14 - 21 / -7:
Perform the division first: 21 / -7 = -3.
Then, subtract the result from 14: 14 - (-3).
Remember that -(-3) is equivalent to +3.
So, the expression becomes 14 + 3 = 17.
7. -5^2:
Start by squaring the number: (-5)^2 = 25.
Since the negative sign is not inside parentheses, it only applies to the number, not the exponent.
8. (-5)^2:
Again, square the number inside parentheses: (-5)^2 = 25.
The parentheses ensure that the negative sign is included in the calculation.
9. -8:
This expression is already in its simplest form, so no further calculations are needed. The answer is -8.
10. -28:
Similarly, this expression is also already simplified to -28.
11. -65:
Again, this expression is already in its simplest form, so no further calculations are required.
12. -13:
This expression is also in its simplest form, so no further calculations are necessary.
13. 1:
Once again, this expression is already in its simplest form.
14. 25:
This expression is also simplified, so no additional calculations are needed.