What is the value of the expression when n=3 -2n(5+n-8-3n)
What is the value of the expression when n=3 -2n(5+n-8-3n)
The Correct Answer and Explanation is:
We are given the expression: −2n(5+n−8−3n)-2n(5 + n – 8 – 3n)
and asked to evaluate it when n=3n = 3. Let’s follow the steps carefully.
Step 1: Simplify the expression inside the parentheses
Start with the inner part of the expression: 5+n−8−3n5 + n – 8 – 3n
Substitute n=3n = 3: 5+3−8−3(3)=5+3−8−95 + 3 – 8 – 3(3) = 5 + 3 – 8 – 9
Now simplify: 8−8−9=0−9=−98 – 8 – 9 = 0 – 9 = -9
Step 2: Multiply by -2n
Now the full expression becomes: −2n(−9)-2n(-9)
Substitute n=3n = 3: −2(3)(−9)=−6×−9=54-2(3)(-9) = -6 \times -9 = 54
✅ Final Answer:
54\boxed{54}
Explanation:
To evaluate the expression −2n(5+n−8−3n)-2n(5 + n – 8 – 3n) when n=3n = 3, we follow the standard order of operations—commonly remembered as PEMDAS (Parentheses, Exponents, Multiplication and Division, Addition and Subtraction).
We begin by simplifying the expression inside the parentheses. This part contains several constants and variables: 5+n−8−3n5 + n – 8 – 3n
Group like terms: combine constants and terms with nn:
- Constants: 5−8=−35 – 8 = -3
- Variable terms: n−3n=−2nn – 3n = -2n
So, the expression simplifies to: −2n(−3−2n)-2n(-3 – 2n)
But we already substituted n=3n = 3, so instead: 5+3−8−9=−95 + 3 – 8 – 9 = -9
Now multiply −2n-2n by this result. First compute −2n-2n with n=3n = 3: −2×3=−6-2 \times 3 = -6
Then: −6×−9=54-6 \times -9 = 54
This illustrates how important it is to simplify the expression in the correct order and substitute values carefully. Errors often occur if we substitute too early or forget negative signs. In this problem, identifying and properly simplifying the expression inside the parentheses is crucial before multiplication. The final result of the whole expression when n=3n = 3 is 54\boxed{54}.
