Evaluate the Expression: Finding the Value of 5x-6 When x=-2

Variable Substitution with Negative Values

What will be the result of this algebraic expression:

5x−6 5x-6

if we place

x=−2 x=-2

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Set up and solve
00:03 Substitute appropriate values according to the given data and solve
00:06 Be careful with parentheses
00:09 Always solve multiplication and division before addition and subtraction
00:12 Positive times negative always equals negative
00:15 Continue solving according to correct order of operations
00:18 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

What will be the result of this algebraic expression:

5x−6 5x-6

if we place

x=−2 x=-2

2

Step-by-step solution

To solve this problem, we will evaluate the algebraic expression 5x−6 5x - 6 by substituting the value of x=−2 x = -2 into it.

Step-by-step solution:

  • Step 1: Substitute x=−2 x = -2 into the expression 5x−6 5x - 6 . This gives:

5(−2)−6 5(-2) - 6

  • Step 2: Perform the operations in the expression. Start with the multiplication:

5(−2)=−10 5(-2) = -10

  • Step 3: Substitute the result of the multiplication back into the expression:

−10−6 -10 - 6

  • Step 4: Now perform the subtraction:

−10−6=−16 -10 - 6 = -16

Therefore, the result of the expression when x=−2 x = -2 is −16 -16 .

Comparing this result with the given choices, we conclude that the correct choice is:

−16 -16

3

Final Answer

−16 -16

Key Points to Remember

Essential concepts to master this topic
  • Substitution Rule: Replace variable with given value in parentheses
  • Technique: Calculate 5(−2)=−10 5(-2) = -10 first, then subtract 6
  • Check: Verify 5(−2)−6=−10−6=−16 5(-2) - 6 = -10 - 6 = -16 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to use parentheses around negative values
    Don't write 5x-2-6 instead of 5(-2)-6 = wrong order of operations! This gives -3 instead of -16. Always put the substituted value in parentheses to maintain proper multiplication.

Practice Quiz

Test your knowledge with interactive questions

What will be the result of this algebraic expression:

\( 5x-6 \)

if we place

\( x=8 \)

FAQ

Everything you need to know about this question

Why do I need parentheses around -2?

+

Parentheses ensure proper order of operations! Without them, 5x−2−6 5x-2-6 becomes confusing. With parentheses, 5(−2)−6 5(-2)-6 clearly shows multiplication first.

What if I get confused with the negative signs?

+

Take it step by step! First: 5×(−2)=−10 5 \times (-2) = -10 . Then: −10−6=−16 -10 - 6 = -16 . Breaking it down prevents sign errors.

How do I know which operation to do first?

+

Follow PEMDAS! Parentheses first, then multiplication 5(−2) 5(-2) , finally subtraction. Always multiply before adding or subtracting.

Can I check my answer somehow?

+

Yes! Substitute back: Does 5(−2)−6=−16 5(-2) - 6 = -16 ? Calculate: −10−6=−16 -10 - 6 = -16 ✓. If both sides match, you're correct!

What if x was positive instead?

+

The process is identical! For x=2 x = 2 : 5(2)−6=10−6=4 5(2) - 6 = 10 - 6 = 4 . Just substitute and follow order of operations.

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