Question

The number of integral values of $b$, for which the equation $x^2+bx-16=0$ has integral roots, is

• A. 2
• B. 3
• C. 4
• D. 5
• E. 6

Answer 1

Answer: (A)

A quadratic equation $x^2+bx-16=0$ have integer roots, when it has following conditions. I. b must be even integer. II. its discriminant is a perfect square of an even number. So, $D=b^2+4.16=b^2+64$ Here, 0 and 6 only the even integers value of b, on which the discriminant of given quadratic equation have perfect square of an even number. So, the number of integral values of b is 2.