Multiple choice

In a quadratic equation with leading coefficient $1$, a student reads the coefficient of $x$ wrongly as $19$ instead of $16$ and obtains the roots as $-15$ and $-4$. The correct roots are

  1. $6, 10$
  2. $-6, -10$
  3. $-7, -9$
  4. $-12, -4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The roots -15 and -4 imply the equation x^2 + 19x + 60 = 0. The student read the coefficient of x wrongly as 19 instead of 16. The correct equation is x^2 + 16x + 60 = 0. Factoring gives (x+6)(x+10) = 0, so the roots are -6 and -10.

AI explanation

Using the incorrect roots of -15 and -4 with the leading coefficient of 1, the student formed the equation (x+15)(x+4) = x^2 + 19x + 60, where 60 is the correct constant term. Since the correct coefficient of x is 16, the actual equation is x^2 + 16x + 60 = 0. Factoring this quadratic equation gives (x+6)(x+10) = 0, which means the correct roots are -6 and -10.