Question

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Answer 1

15 + 2s - s² = 0

shifting everything to RHS, we get–

s² - 2s - 15 = 0

s² - 5s + 3s - 15 = 0

s(s - 5) + 3(s - 5) = 0

(s + 3)(s - 5) = 0

s + 3 = 0 => s = -3

OR

s - 5 = 0 => s = 5

Hence, s = -3 or s = 5 satisfies the given equation.