Which factored form represents \(x^2+9x+20=0\)?
Answer and explanation
Correct answer: (x+4)(x+5)=0
Method: find two numbers whose product is 20 and sum is 9. The pair 4 and 5 satisfy \(4\cdot5=20\) and \(4+5=9\), so the factorization is \((x+4)(x+5)=0\). Option B would use -4 and -5 giving sum \(-9\), so it is incorrect. Options C and D sum to 12 and 21 respectively, so they do not match the middle coefficient. Exam tip: list factor pairs of the constant term (20 = 1·20, 2·10, 4·5) and pick the pair whose sum equals the coefficient of \(x\).
Frequently asked questions
What is the correct answer to this question?
(x+4)(x+5)=0
Why is this the correct answer?
Method: find two numbers whose product is 20 and sum is 9. The pair 4 and 5 satisfy \(4\cdot5=20\) and \(4+5=9\), so the factorization is \((x+4)(x+5)=0\). Option B would use -4 and -5 giving sum \(-9\), so it is incorrect. Options C and D sum to 12 and 21 respectively, so they do not match the middle coefficient. Exam tip: list factor pairs of the constant term (20 = 1·20, 2·10, 4·5) and pick the pair whose sum equals the coefficient of \(x\).
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Introduction to Quadratic Equations.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
