If the roots of the equation \(x^2-12x+k=0\) are real and distinct, what is the correct condition on \(k\)?
Answer and explanation
Correct answer: \(k<36\)
For a quadratic equation \(ax^2+bx+c=0\), the roots are real and distinct only when the discriminant \(D=b^2-4ac\) is greater than zero. Here, \(a=1\), \(b=-12\), and \(c=k\), so \(D=(-12)^2-4(1)(k)=144-4k>0\). Therefore, \(k<36\). When \(k=36\), the roots are equal, so that option is not correct. Exam tip: For “real and distinct” roots, always apply \(D>0\).
Frequently asked questions
What is the correct answer to this question?
\(k<36\)
Why is this the correct answer?
For a quadratic equation \(ax^2+bx+c=0\), the roots are real and distinct only when the discriminant \(D=b^2-4ac\) is greater than zero. Here, \(a=1\), \(b=-12\), and \(c=k\), so \(D=(-12)^2-4(1)(k)=144-4k>0\). Therefore, \(k<36\). When \(k=36\), the roots are equal, so that option is not correct. Exam tip: For “real and distinct” roots, always apply \(D>0\).
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Introduction to Quadratic Equations.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
