allerySolve by quadratic formula: x^2 - 4x - 5 = 0. Roots are
A-5 and -1
B-5 and 1
C5 and 1
D5 and -1
Answer & Solution
Correct answer: D. 5 and -1
1. a = 1, b = -4, c = -5.
2. D = 16 + 20 = 36, sqrt(D) = 6.
3. x = (4 plus or minus 6) / 2.
4. So x = 5 or x = -1.
_Source: Selina Concise Mathematics Class 10, Ch 5 Quadratic Equations (Mistral OCR'd PDF), section on quadratic formula_
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