Compare Expressions: Finding Equivalence in (6b+3)(a-2) and Related Forms

Algebraic Expansion with Expression Comparison

Which of the following expressions have the same value?

  1. (6b+3)(2+a) (6b+3)(-2+a)

  2. (2b+1)(3a6) (2b+1)(3a-6)

  3. (a+3)(6b2) (a+3)(6b-2)

  4. 6ab+3a12b6 6ab+3a-12b-6

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Choose which expressions are equal
00:09 Break down 6 into factors 3 and 2
00:17 Take out the common factors from the parentheses
00:33 This is the simplification for a, now let's simplify b
00:46 Let's calculate the multiplication
00:55 We can see that the expressions are equal
00:58 Let's move to d
01:05 Break down 6 into factors 3 and 2
01:09 Break down 12 into factors 3, 2, and 2
01:17 Take out the common factors from the parentheses
01:27 We can see that the expressions are equal
01:34 Now let's move to c
01:40 Open parentheses correctly
01:45 We can see it's not equal to the other expressions
01:50 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

Which of the following expressions have the same value?

  1. (6b+3)(2+a) (6b+3)(-2+a)

  2. (2b+1)(3a6) (2b+1)(3a-6)

  3. (a+3)(6b2) (a+3)(6b-2)

  4. 6ab+3a12b6 6ab+3a-12b-6

2

Step-by-step solution

To solve this problem, we need to systematically expand and simplify each expression given in the problem statement:

  • Expression 1: (6b+3)(2+a) (6b+3)(-2+a)

    Expand using the distributive property:

    =6b(2)+6b(a)+3(2)+3(a) = 6b(-2) + 6b(a) + 3(-2) + 3(a)

    =12b+6ab6+3a = -12b + 6ab - 6 + 3a

    Reorder terms: 6ab+3a12b6 6ab + 3a - 12b - 6

  • Expression 2: (2b+1)(3a6) (2b+1)(3a-6)

    Expand using the distributive property:

    =2b(3a)+2b(6)+1(3a)+1(6) = 2b(3a) + 2b(-6) + 1(3a) + 1(-6)

    =6ab12b+3a6 = 6ab - 12b + 3a - 6

    This simplifies directly to 6ab+3a12b6 6ab + 3a - 12b - 6

  • Expression 3: (a+3)(6b2) (a+3)(6b-2)

    Expand using the distributive property:

    =a(6b)+a(2)+3(6b)+3(2) = a(6b) + a(-2) + 3(6b) + 3(-2)

    =6ab2a+18b6 = 6ab - 2a + 18b - 6

    This results in 6ab2a+18b6 6ab - 2a + 18b - 6 , clearly different from the others

  • Expression 4: 6ab+3a12b6 6ab+3a-12b-6

    This is already simplified and the same as the results of expressions 1 and 2.

Upon comparing the simplified expressions, expressions 1, 2, and 4 have the same value: 6ab+3a12b6 6ab + 3a - 12b - 6 . Expression 3 differs with 6ab2a+18b6 6ab - 2a + 18b - 6 .

Thus, the expressions with the same value are 1, 2, and 4.

Therefore, the correct answer is choice 4: 1,2,4 1,2,4 .

3

Final Answer

1,2,4 1,2,4

Key Points to Remember

Essential concepts to master this topic
  • Rule: Use distributive property to expand all binomial products systematically
  • Technique: For (6b+3)(-2+a), multiply each term: 6b(-2) + 6b(a) + 3(-2) + 3(a)
  • Check: Compare expanded forms by arranging terms in standard order: 6ab + 3a - 12b - 6 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to distribute to all terms
    Don't multiply (6b+3)(-2+a) as just 6b(-2) + 3(a) = wrong expansion! This skips half the multiplication and gives incorrect results. Always multiply each term in the first binomial by each term in the second binomial.

Practice Quiz

Test your knowledge with interactive questions

Break down the expression into basic terms:

\( 4x^2 + 6x \)

FAQ

Everything you need to know about this question

How do I remember to multiply every term?

+

Use the FOIL method for binomials: First terms, Outer terms, Inner terms, Last terms. For (6b+3)(-2+a), that's 6b(-2), 6b(a), 3(-2), 3(a).

Why does the order of terms matter when comparing?

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The order doesn't change the value, but arranging terms consistently makes comparison much easier! Always write in standard form: variables with highest degree first, then constants.

What if I get different signs when expanding?

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Pay careful attention to negative signs! When you have (-2+a), the negative applies to 2, not a. Double-check each multiplication step.

How can I verify my expansions are correct?

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Substitute simple values like a=1, b=1 into both the original and expanded forms. If you get the same result, your expansion is likely correct!

Can expressions look different but still be equal?

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Absolutely! (6b+3)(2+a) (6b+3)(-2+a) and (2b+1)(3a6) (2b+1)(3a-6) look completely different but both equal 6ab+3a12b6 6ab + 3a - 12b - 6 when expanded.

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