When first applying ( (2x+1)(2x+9) ) in ( (2x+1)(2x+5)(2x+9) ), what is obtained?
Answer and explanation
Correct answer: \(4x^2+20x+9\)
First multiply the two outer binomials: \((2x+1)(2x+9)=4x^2+18x+2x+9=4x^2+20x+9\). Therefore, option A is correct. In option B, the middle terms from \(2x\cdot9\) and \(1\cdot2x\) have not been added correctly. Exam tip: write all four products before combining like terms.
Frequently asked questions
What is the correct answer to this question?
\(4x^2+20x+9\)
Why is this the correct answer?
First multiply the two outer binomials: \((2x+1)(2x+9)=4x^2+18x+2x+9=4x^2+20x+9\). Therefore, option A is correct. In option B, the middle terms from \(2x\cdot9\) and \(1\cdot2x\) have not been added correctly. Exam tip: write all four products before combining 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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