JAMB 2011 Mathematics · Question 44

Factorize completely 9y2 - 16X2

Options

  1. A.(3y - 2x)(3y + 4x)
  2. B.(3y + 4x)(3y + 4x)
  3. C.(3y + 2x)(3y - 4x)
  4. D.(3y - 4x)(3y + 4x)

Answer: D. (3y - 4x)(3y + 4x)

Explanation written with AI and checked against the answer key

Analysis

The expression given is 9y2−16x29y^2 - 16x^2. This is a classic algebraic expression that fits the Difference of Two Squares pattern.

Concept: Difference of Two Squares

In algebra, the difference of two squares follows the identity:

a2−b2=(a−b)(a+b)a^2 - b^2 = (a - b)(a + b)

To solve this, we need to express both terms in the given expression as perfect squares.

Step-by-Step Solution
  1. Identify the squares: • The first term is 9y29y^2. Since 9=329 = 3^2, we can write this as (3y)2(3y)^2. • The second term is 16x216x^2. Since 16=4216 = 4^2, we can write this as (4x)2(4x)^2.
  1. Rewrite the expression: Substituting these back into the original expression, we get: $(3y)2−(4x)2(3y)^2 - (4x)^2$
  1. Apply the identity: Using the formula a2−b2=(a−b)(a+b)a^2 - b^2 = (a - b)(a + b), where a=3ya = 3y and b=4xb = 4x: $(3y−4x)(3y+4x)(3y - 4x)(3y + 4x)$
Conclusion

Comparing our result (3y−4x)(3y+4x)(3y - 4x)(3y + 4x) with the given options, it matches option D.

Exam Tip

Whenever you see a binomial (two terms) with a minus sign between them, always check if both terms are perfect squares (like 1, 4, 9, 16, 25, 36, etc.). If they are, you can immediately use the (a−b)(a+b)(a-b)(a+b) shortcut to save time during your JAMB exam!

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