What is the standard form of \((x-4)(x+1)=0\)?
Answer and explanation
Correct answer: \(x^2-3x-4=0\)
Expanding gives \((x-4)(x+1)=x^2+x-4x-4=x^2-3x-4\), so the standard form is \(x^2-3x-4=0\). Quick check: the roots are 4 and −1, their sum is 3, and since −b/a = 3 we must have b = −3. The closest distractor (option B) typically arises from a sign mistake on the linear term; the other options have wrong signs or constant term. Exam tip: combine like terms immediately after multiplying and verify using sum/product of roots.
Frequently asked questions
What is the correct answer to this question?
\(x^2-3x-4=0\)
Why is this the correct answer?
Expanding gives \((x-4)(x+1)=x^2+x-4x-4=x^2-3x-4\), so the standard form is \(x^2-3x-4=0\). Quick check: the roots are 4 and −1, their sum is 3, and since −b/a = 3 we must have b = −3. The closest distractor (option B) typically arises from a sign mistake on the linear term; the other options have wrong signs or constant term. Exam tip: combine like terms immediately after multiplying and verify using sum/product of roots.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Introduction to Quadratic Equations.
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