What is the answer for ( 98^2 ) using ( (100-2)^2 )?
Answer and explanation
Correct answer: 9604
Write 98 as \(100-2\). Using \((a-b)^2=a^2-2ab+b^2\), \((100-2)^2=100^2-2\times100\times2+2^2=10000-400+4=9604\). Therefore, 9604 is correct. In 9804, the middle-term subtraction has not been handled correctly. Exam tip: in \((a-b)^2\), the middle term is \(-2ab\), so keep its negative sign.
Frequently asked questions
What is the correct answer to this question?
9604
Why is this the correct answer?
Write 98 as \(100-2\). Using \((a-b)^2=a^2-2ab+b^2\), \((100-2)^2=100^2-2\times100\times2+2^2=10000-400+4=9604\). Therefore, 9604 is correct. In 9804, the middle-term subtraction has not been handled correctly. Exam tip: in \((a-b)^2\), the middle term is \(-2ab\), so keep its negative sign.
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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