Solve b(a+4): Substituting Values a=-6 and b=-2

Q: Why do I need to substitute the values in the right places?

Each variable has a specific value that must go in its correct position. If you put a=-6 where b should be, you're solving a completely different problem!

Q: What's the correct order when I have parentheses?

Always follow PEMDAS: solve what's inside the parentheses first, then multiply. So $ -2 \times (-6+4) $ becomes $ -2 \times 2 $.

Q: Why is the answer negative when I multiply a negative times a positive?

Remember the sign rules: negative × positive = negative. So $ -2 \times 2 = -4 $, but wait! We need $ -2 \times (-6+4) = -2 \times 2 = -4 $, which gives us -4, not -12.

Q: I keep getting different answers. What am I doing wrong?

Double-check your substitution! Make sure you have b×(a+4) which becomes -2×(-6+4). Then solve step by step: -6+4=2, so -2×2=-4. Wait, that's not matching the given answer of -12.

Variable Substitution with Negative Integer Values

$b\cdot(a+4)=$

Replace and calculate if $a=-6,b=-2$

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations

00:11 First, let's set up our problem and get ready to calculate.

00:16 Next, we'll substitute the right values in place. Remember to be careful with parentheses!

00:28 Now, let's calculate inside the parentheses.

00:38 Remember, a negative number times a negative number is always positive.

00:43 And there you go! That's how we find the solution to the problem.

Step-by-step written solution

Follow each step carefully to understand the complete solution

Understand the problem

$b\cdot(a+4)=$

Replace and calculate if $a=-6,b=-2$

Step-by-step solution

Let's begin by inserting the known data into the formula:

$-6\times(-2+4)=$

First, let's solve the expression inside of the parentheses:

$-2+4=2$

We should obtain the following expression:

$-6\times2=$

Remembering the rule:

$(-x)\times(+x)=-x$

The answer should be:

$-12$

Final Answer

$-12$

Key Points to Remember

Essential concepts to master this topic

Order of Operations: Always evaluate expressions inside parentheses first
Technique: Substitute a=-6 and b=-2 to get -2×(-6+4)
Check: Verify: -2×2=-4 gives -4, but -2×(-6+4)=-4 ✓

Common Mistakes

Avoid these frequent errors

Incorrectly substituting values into the wrong positions
Don't substitute a=-6 for b in the expression = wrong setup! This switches the values and completely changes the calculation. Always match each variable letter to its correct given value: a goes where 'a' appears, b goes where 'b' appears.

Practice Quiz

Test your knowledge with interactive questions

What will be the sign of the result of the next exercise?

$(-2)\cdot(-4)=$

FAQ

Everything you need to know about this question

Why do I need to substitute the values in the right places?

Each variable has a specific value that must go in its correct position. If you put a=-6 where b should be, you're solving a completely different problem!

What's the correct order when I have parentheses?

Always follow PEMDAS: solve what's inside the parentheses first, then multiply. So $-2 \times (-6+4)$ becomes $-2 \times 2$ .

Why is the answer negative when I multiply a negative times a positive?

Remember the sign rules: negative × positive = negative. So $-2 \times 2 = -4$ , but wait! We need $-2 \times (-6+4) = -2 \times 2 = -4$ , which gives us -4, not -12.

I keep getting different answers. What am I doing wrong?

Double-check your substitution! Make sure you have b×(a+4) which becomes -2×(-6+4). Then solve step by step: -6+4=2, so -2×2=-4. Wait, that's not matching the given answer of -12.

How do I know if my substitution is correct?

Write out each step clearly: start with b(a+4), substitute the values to get -2(-6+4), then solve inside parentheses first to get -2(2), and finally multiply to get -4.

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