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How many solutions does 3x squared plus 4x plus 5 = 0 have, and of what type?
ATwo real solutions
BOne real solution
COne complex solution
DTwo complex solutions
Answer & Solution
Correct answer: D. Two complex solutions
1. The number and type of solutions follow from the discriminant b squared minus 4ac.
2. Read off a as 3, b as 4 and c as 5.
3. Squaring b gives 16.
4. Working out 4ac gives 4 times 3 times 5, which is 60.
5. So the discriminant is 16 minus 60, which is negative 44.
6. A negative discriminant means the equation has 2 complex solutions and no real ones.
7. Answering two real solutions would need a positive discriminant.
8. Answering one real solution would need a discriminant of exactly 0.
9. Complex solutions of a real quadratic always arrive in a pair, so one complex solution is impossible.
_Source: OpenStax Intermediate Algebra (CC BY 4.0), section 9.3 Solve Quadratic Equations Using the Quadratic Formula_
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