0 reads0 ratings0 helpful
Which of the following expressions can be factorised over integers using the identity for the difference of two squares?
Advertisement
Answer and explanation
Correct answer: \(x^2-81\)
\(x^2-81=x^2-9^2\), so using \(a^2-b^2=(a-b)(a+b)\), it becomes \((x-9)(x+9)\). \(x^2+81\) is a sum of squares, not a difference of squares over integers. Exam tip: check for two perfect squares with a minus sign.
Frequently asked questions
What is the correct answer to this question?
\(x^2-81\)
Why is this the correct answer?
\(x^2-81=x^2-9^2\), so using \(a^2-b^2=(a-b)(a+b)\), it becomes \((x-9)(x+9)\). \(x^2+81\) is a sum of squares, not a difference of squares over integers. Exam tip: check for two perfect squares with a minus sign.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Factorisation.
Student feedback
Was this question useful?
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Difficulty
Easy0%
Medium0%
Hard0%
Was the explanation clear?
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
Advertisement