What is the expanded form of ((2x+1)(x-4))?
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Answer and explanation
Correct answer: \(2x^2-7x-4\)
Use the distributive property: \((2x+1)(x-4)=2x\cdot x+2x\cdot(-4)+1\cdot x+1\cdot(-4)\). Thus, \(2x^2-8x+x-4=2x^2-7x-4\), so option A is correct. In option B, \(-8x+x\) has incorrectly been treated as \(+7x\). Exam tip: write all four products first, then combine only like terms.
Frequently asked questions
What is the correct answer to this question?
\(2x^2-7x-4\)
Why is this the correct answer?
Use the distributive property: \((2x+1)(x-4)=2x\cdot x+2x\cdot(-4)+1\cdot x+1\cdot(-4)\). Thus, \(2x^2-8x+x-4=2x^2-7x-4\), so option A is correct. In option B, \(-8x+x\) has incorrectly been treated as \(+7x\). Exam tip: write all four products first, then combine only like terms.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Quadratic expressions.
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