What is the value of (15^2-9^2)?
Answer and explanation
Correct answer: 144
Use the identity \(a^2-b^2=(a-b)(a+b)\). Thus, \(15^2-9^2=(15-9)(15+9)=6\times24=144\). Therefore, 144 is the correct answer. A value such as 154 can result from an error in subtraction or multiplication. Exam tip: For expressions involving a difference of squares, use the identity instead of calculating both squares separately.
Frequently asked questions
What is the correct answer to this question?
144
Why is this the correct answer?
Use the identity \(a^2-b^2=(a-b)(a+b)\). Thus, \(15^2-9^2=(15-9)(15+9)=6\times24=144\). Therefore, 144 is the correct answer. A value such as 154 can result from an error in subtraction or multiplication. Exam tip: For expressions involving a difference of squares, use the identity instead of calculating both squares separately.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems. Topic: Exponents.
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