For any real constant \(k\), what is the nature of the roots of the equation \(9x^2-6(k-1)x+(k-1)^2=0\)?

Correct answer: Always real and equal

Here, \(a=9\), \(b=-6(k-1)\), and \(c=(k-1)^2\). Therefore, the discriminant is \(D=b^2-4ac=[-6(k-1)]^2-4(9)(k-1)^2=0\). Hence, for every real value of \(k\), the roots are real and equal. The equation can also be written as \([3x-(k-1)]^2=0\). Even when \(k=1\), it becomes \(9x^2=0\), which is still a quadratic equation. Exam tip: When \(D=0\), the roots are real and equal.