SOLUTION: Please help me help my daughter with this equation: 12-(20-2(6^2/3*2^2) I have seen the solution but don't understand how you get there. How does one know to multiply the inner p

Algebra ->  Expressions -> SOLUTION: Please help me help my daughter with this equation: 12-(20-2(6^2/3*2^2) I have seen the solution but don't understand how you get there. How does one know to multiply the inner p      Log On


   

Question 6939: Please help me help my daughter with this equation:
12-(20-2(6^2/3*2^2) I have seen the solution but don't understand how you get there.
How does one know to multiply the inner parenthesis by -2 rather than by 18, 20-2?
In the solution, both the 6^2 and 2^2 are divided by 3, then multiplied, rather than 6^2 divided by 3 and then multiplied by 2^2. Why is this?
In the solution the minus sign behind the 20 becomes a plus sign, why?
Thank you.
Answer by glabow(165) About Me  (Show Source):
You can put this solution on YOUR website!
The rules for evaluating expressions is:
Do all operations in a group, identified by parentheses. Once all groups are evaluated, evaluate the expression.
For all evaluations, do powers and roots first.
Second, do all multiplication and division.
Third, do all addition and subtraction.
Let's evaluate your expression.
12-%2820-2%28%286%5E2%29%2F3%292%5E2%29
There is a group %286%5E2%2F3%29 that must be done first. 36/3 = 12.
This gives 12-%2820-2%2812%292%5E2%29
There is a power that must be done next. 2%5E2+=+4.
This gives 12-%2820-2%2812%294%29
Now do all multiplication, 2(12)(4)=96.
This gives 12-%2820-96%29
There is a group (20-96) that must be done. This gives
12+-+%28-76%29
Subtracting a negative number is the same as adding a positive one. This gives
12+%2B+76+=+88. DONE!
Subtraction is really adding the negative of a number. That is,
a - b is really a + (-b). What we had above was
12 - (-76) is really 12 + (-(-76)). The negative of a negative number is the positive of the number. So it's really 12 + 76.