What is the value of ( 998^2 ) using ( (1000-2)^2 )?
Answer and explanation
Correct answer: 996004
Write 998 as \(1000-2\). Using \((a-b)^2=a^2-2ab+b^2\), we get \((1000-2)^2=1000^2-2\times1000\times2+2^2=1000000-4000+4=996004\). Therefore, option A is correct. Option D misses the final \(+4\) term. Exam tip: the middle term in \((a-b)^2\) is always negative.
Frequently asked questions
What is the correct answer to this question?
996004
Why is this the correct answer?
Write 998 as \(1000-2\). Using \((a-b)^2=a^2-2ab+b^2\), we get \((1000-2)^2=1000^2-2\times1000\times2+2^2=1000000-4000+4=996004\). Therefore, option A is correct. Option D misses the final \(+4\) term. Exam tip: the middle term in \((a-b)^2\) is always negative.
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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