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If 5x + 3y=4 and 5x-3y= 2, what is the value of (25x\(^2\) -9y\(^2\))?

Mathematics
WAEC 2022

If 5x + 3y=4 and 5x-3y= 2, what is the value of (25x\(^2\) -9y\(^2\))?

  • A. 20
  • B. 16
  • C. 2
  • D. 8
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Correct Answer: Option D
Explanation

5x + 3y=4

5x-3y= 2

Using elimination method 

5x + 3y=4 →    5x + 3y=4

-[5x-3y= 2] → -5x +3y= -2

6y = 2 

y → 1/3 and x = 3/5

solving (25x\(^2\) -9y\(^2\))

25 * [3/5]\(^2\) -9 * [1/3]\(^2\)

25 * \(\frac{9}{25}\) - 9 \(\frac{1}{9}\)

9 - 1 = 8

 


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WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC offline past questions - with all answers and explanations in one app - Download for free
WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995