( 9x^2-30x+25 ) is the perfect square of what?
Answer and explanation
Correct answer: \((3x-5)^2\)
Use the identity \((a-b)^2=a^2-2ab+b^2\). Taking \(a=3x\) and \(b=5\), we get \((3x-5)^2=9x^2-30x+25\). In option A, the middle term would be \(+30x\), so it is not correct. Exam tip: take the square roots of the first and last terms, then verify the middle term using \(\pm2ab\).
Frequently asked questions
What is the correct answer to this question?
\((3x-5)^2\)
Why is this the correct answer?
Use the identity \((a-b)^2=a^2-2ab+b^2\). Taking \(a=3x\) and \(b=5\), we get \((3x-5)^2=9x^2-30x+25\). In option A, the middle term would be \(+30x\), so it is not correct. Exam tip: take the square roots of the first and last terms, then verify the middle term using \(\pm2ab\).
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Algebraic identities.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
