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Algebra Difficulty 3.2 AMC 10/12 Find the answer

Is there a line ll passing through the point (5,4)(-5, -4) such that it forms a triangle with the two coordinate axes with an area of 5? If it exists, find the equation of line ll in the standard form of a linear equation; if it does not exist, explain why.

A number or a short expression. Spacing and $ signs are ignored.

Solution

Assume there exists a line ll passing through the point (5,4)(-5, -4),
such that it forms a triangle with the two coordinate axes with an area of 5.
Let the equation of line ll be: xa+yb=1,\frac{x}{a} + \frac{y}{b} = 1,
then 5a+4b=1.\frac{-5}{a} + \frac{-4}{b} = 1. This simplifies to 4a+5b+ab=0.4a + 5b + ab = 0. The area S=12ab=5,S = \frac{1}{2}|ab| = 5, which simplifies to ab=10.|ab| = 10.
Combining {4a+5b+ab=0ab=10,\begin{cases} 4a + 5b + ab = 0 \\ |ab| = 10 \end{cases},
we get {a=52b=4\begin{cases} a = -\frac{5}{2} \\ b = 4 \end{cases} or {a=5b=2.\begin{cases} a = 5 \\ b = -2 \end{cases}.
Therefore, there exists a line ll with the equations 8x5y+20=08x - 5y + 20 = 0 or 2x5y10=0.2x - 5y - 10 = 0.

Thus, the final answer is 8x5y+20=0 or 2x5y10=0\boxed{8x - 5y + 20 = 0 \text{ or } 2x - 5y - 10 = 0}.

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.