Advanced Math practice question

Answer: 8

n(n − 3)/2 = 20 → n² − 3n − 40 = 0 → (n − 8)(n + 5) = 0 → n = 8.

Common wrong answers

If you answered 5

5 gives 5(2)/2 = 5 diagonals.

If you answered 10

10 gives 10(7)/2 = 35 diagonals.

If you answered -5

−5 is the rejected negative root.

More Advanced Math questions

• Hard
  A population of bacteria doubles every 3 hours. If it starts at 500, which function models the population P af…
• Hard
  How many real solutions does x² + 4x + 5 = 0 have?
• Hard
  A car worth $20,000 loses 15% of its value each year. What is its value after 2 years?
• Hard
  An investment of $1,000 grows at 6% per year, compounded annually. Which expression gives its value after t ye…
• Hard
  If f(x) = x² − 1 and g(x) = x + 2, what is g(f(3))?
• Hard
  The parabola y = x² − 8x + 12 crosses the x-axis at two points. What is the x-coordinate of the vertex?