If \(p(x)=x^2-2x+5\), why are its zeroes not real?
Answer and explanation
Correct answer: \(D<0\)
For a quadratic, the discriminant is \(D=b^2-4ac\). Here \(a=1,\;b=-2,\;c=5\), so \(D=(-2)^2-4\cdot1\cdot5=4-20=-16\), which is negative. When \(D<0\) the quadratic has no real roots; instead it has a pair of complex conjugate roots. The closest distractor \(D>0\) and not a perfect square would imply two distinct real (typically irrational) roots, so it does not apply here. Exam tip: compute \(D\) quickly — sign of \(D\) decides real vs. repeated vs. complex roots.
Frequently asked questions
What is the correct answer to this question?
\(D<0\)
Why is this the correct answer?
For a quadratic, the discriminant is \(D=b^2-4ac\). Here \(a=1,\;b=-2,\;c=5\), so \(D=(-2)^2-4\cdot1\cdot5=4-20=-16\), which is negative. When \(D<0\) the quadratic has no real roots; instead it has a pair of complex conjugate roots. The closest distractor \(D>0\) and not a perfect square would imply two distinct real (typically irrational) roots, so it does not apply here. Exam tip: compute \(D\) quickly — sign of \(D\) decides real vs. repeated vs. complex roots.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Polynomials. Topic: Irrational numbers and real numbers.
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