What are the roots of the equation \(x^2+12x+8=0\)?
Answer and explanation
Correct answer: \(x=-6\pm2\sqrt{7}\)
Completing the square gives \(x^2+12x+8=0\Rightarrow (x+6)^2=28\). Therefore, \(x+6=\pm\sqrt{28}=\pm2\sqrt{7}\), so the roots are \(x=-6\pm2\sqrt{7}\). Option B has the wrong sign for the constant term in the roots. Exam tip: simplify \(\sqrt{28}\) to \(2\sqrt{7}\).
Frequently asked questions
What is the correct answer to this question?
\(x=-6\pm2\sqrt{7}\)
Why is this the correct answer?
Completing the square gives \(x^2+12x+8=0\Rightarrow (x+6)^2=28\). Therefore, \(x+6=\pm\sqrt{28}=\pm2\sqrt{7}\), so the roots are \(x=-6\pm2\sqrt{7}\). Option B has the wrong sign for the constant term in the roots. Exam tip: simplify \(\sqrt{28}\) to \(2\sqrt{7}\).
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Methods of Solving Quadratic Equations.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
