CA Foundation · Quantitative Aptitude · Equations
If one root of the quadratic equation x² − 7x + k = 0 is 3, what is the other root?
The other root is 4. For x² − 7x + k = 0 the sum of the roots equals 7, so with one root equal to 3 the remaining root is 7 minus 3, which is 4. This also gives k = 12.
- A3
- B4Correct
- C10
- D−4
Explanation
Sum of roots = 7. One root is 3, so the other is 7 − 3 = 4. Check: k = 3 × 4 = 12, and 3² − 21 + 12 = 0. Taking 7 + 3 = 10 wrongly adds the known root instead of subtracting it.
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