When first applying ( (2x+1)(2x+5) ) in ( (2x+1)(2x+3)(2x+5) ), what is obtained?
Answer and explanation
Correct answer: \(4x^2+12x+5\)
On multiplying \((2x+1)(2x+5)\), we get \(2x\cdot2x=4x^2\), the cross terms \(2x\cdot5+1\cdot2x=12x\), and \(1\cdot5=5\). Therefore, the result is \(4x^2+12x+5\). Option B has an incorrect sum of the middle terms. Exam tip: write all four products while multiplying two binomials, then combine like terms.
Frequently asked questions
What is the correct answer to this question?
\(4x^2+12x+5\)
Why is this the correct answer?
On multiplying \((2x+1)(2x+5)\), we get \(2x\cdot2x=4x^2\), the cross terms \(2x\cdot5+1\cdot2x=12x\), and \(1\cdot5=5\). Therefore, the result is \(4x^2+12x+5\). Option B has an incorrect sum of the middle terms. Exam tip: write all four products while multiplying two binomials, then combine like terms.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Algebraic identities.
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