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Omni-MATH / Let a₁,a₂,… be an arithmetic sequence and b₁,b₂,… be a geometric sequence. Suppose that a₁b₁=20, a₂b₂=19, and a₃b₃=14. Find the greatest possible value of a₄b₄.

Problem

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problem

Let a1,a2,…a_{1}, a_{2}, \ldots be an arithmetic sequence and b1,b2,…b_{1}, b_{2}, \ldots be a geometric sequence. Suppose that a1b1=20a_{1} b_{1}=20, a2b2=19a_{2} b_{2}=19, and a3b3=14a_{3} b_{3}=14. Find the greatest possible value of a4b4a_{4} b_{4}.
Plain-text mathematical notation (without MathML)
Let a₁,a₂,… be an arithmetic sequence and b₁,b₂,… be a geometric sequence. Suppose that a₁b₁=20, a₂b₂=19, and a₃b₃=14. Find the greatest possible value of a₄b₄.
Original LaTeX notation
Let $a_{1}, a_{2}, \ldots$ be an arithmetic sequence and $b_{1}, b_{2}, \ldots$ be a geometric sequence. Suppose that $a_{1} b_{1}=20$, $a_{2} b_{2}=19$, and $a_{3} b_{3}=14$. Find the greatest possible value of $a_{4} b_{4}$.

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