What is the expansion of ( (x-4)(x+9) )?
Answer and explanation
Correct answer: \(x^2+5x-36\)
Use the distributive property: \((x-4)(x+9)=x^2+9x-4x-36=x^2+5x-36\). Therefore, option B is correct. In option A, the middle terms have incorrectly been treated as \(9x+4x\) instead of \(9x-4x\). Exam tip: while combining like terms, check the signs carefully.
Frequently asked questions
What is the correct answer to this question?
\(x^2+5x-36\)
Why is this the correct answer?
Use the distributive property: \((x-4)(x+9)=x^2+9x-4x-36=x^2+5x-36\). Therefore, option B is correct. In option A, the middle terms have incorrectly been treated as \(9x+4x\) instead of \(9x-4x\). Exam tip: while combining like terms, check the signs carefully.
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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