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Let a, b be integers such that all the roots of the equation (x2 + ax + 20)(a2 + 17x + b) = 0 are negative integers. What is the smallest possible value of a + b? |
Answer» ∵ Roots of (x2 + ax + 20)(a2 + 17x + b) = 0 are negative integers and we required (a + b)min ∴ a, b each should be minimum a2 – 80 is perfect square and a is a positive integer ⇒ amin = 9 289 – 4b is a perfect square and b is a positive integer ⇒ bmin = 16 (using 8, 15, 17) ∴ (a + b)min = 25 |
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