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Q: Three times the square of a number subtracting by 4 times the number is equal to 50 more than the number. Find the number.
  • A. 5
  • B. 4
  • C. 6
  • D. 10
Correct Answer: Option A - Let the number be = x According to the question, 3x² – x × 4 = x + 50 3x² – 4x – x – 50 = 0 3x² – 5x – 50 = 0 3x² – 15x + 10x – 50 = 0 3x (x – 5) + 10 (x – 5) = 0 (x – 5) (3x + 10) = 0 x – 5 = 0 x = 5
A. Let the number be = x According to the question, 3x² – x × 4 = x + 50 3x² – 4x – x – 50 = 0 3x² – 5x – 50 = 0 3x² – 15x + 10x – 50 = 0 3x (x – 5) + 10 (x – 5) = 0 (x – 5) (3x + 10) = 0 x – 5 = 0 x = 5

Explanations:

Let the number be = x According to the question, 3x² – x × 4 = x + 50 3x² – 4x – x – 50 = 0 3x² – 5x – 50 = 0 3x² – 15x + 10x – 50 = 0 3x (x – 5) + 10 (x – 5) = 0 (x – 5) (3x + 10) = 0 x – 5 = 0 x = 5