What condition on \(m\) is necessary for the equation \(x^2-(m+3)x+3m=0\) to have two real and distinct roots?
Answer and explanation
Correct answer: \(m\ne 3\)
A quadratic equation has two real and distinct roots only when its discriminant satisfies \(D>0\). Here, \(D=(m+3)^2-4(1)(3m)=m^2-6m+9=(m-3)^2\). This is zero when \(m=3\) and positive for every other real value of \(m\). Therefore, the required condition is \(m\ne3\). In option B, the roots are real but equal, not distinct. Exam tip: use \(D>0\) for distinct real roots, \(D=0\) for equal roots, and \(D<0\) for non-real roots.
Frequently asked questions
What is the correct answer to this question?
\(m\ne 3\)
Why is this the correct answer?
A quadratic equation has two real and distinct roots only when its discriminant satisfies \(D>0\). Here, \(D=(m+3)^2-4(1)(3m)=m^2-6m+9=(m-3)^2\). This is zero when \(m=3\) and positive for every other real value of \(m\). Therefore, the required condition is \(m\ne3\). In option B, the roots are real but equal, not distinct. Exam tip: use \(D>0\) for distinct real roots, \(D=0\) for equal roots, and \(D<0\) for non-real roots.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Nature of Roots.
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