Thanks for the responses, everyone!
I googled to find the geometric representations of AlephZero's squared binomials and found this site:
http://pespmc1.vub.ac.be/POS/Turchap11.html
Where the cause of the limits of Greek math is laid on the doorstep of Platonic thinking:
"THE GREEKS' failure to create algebra is profoundly rooted in their philosophy. They did not even have arithmetic algebra. Arithmetic equations held little interest for them: after all, even quadratic equations do not, generally speaking, have exact numerical solutions. And approximate calculations and everything bound up with practical problems were uninteresting to them. On the other hand, the solution could have been found by geometric construction! But even if we assume that the Greek mathematicians of the Platonic school were familiar with arithmetic letter symbols it is difficult to imagine that they would have performed Descartes' scientific feat. To the Greeks relations were not ideas and therefore did not have real existence. Who would ever think of using a letter to designate something that does not exist? The Platonic idea is a generalized image. a form a characteristic: it can be pictured in the imagination as a more or less generalized object. All this is primary and has independent existence an existence even more real than that of things perceived by the senses. But what is a relation of line segments? Try to picture it and you will immediately see that what you are picturing is precisely two line segments, not any kind of relation. The concept of the relation of quantities reflects the process of measuring one by means of the other. But the process is not an idea in the Platonic sense: it is something secondary that does not really exist. Ideas are eternal and invariable, and by this alone have nothing in common with processes.
Interestingly. the concept of the relation of quantities, which reflects characteristics of the measurement process, was introduced in strict mathematical form as early as Eudoxus and was included in the fifth book of Euclid's Elements. This was exactly the concept Descartes used. But the relation as an object is not found in Eudoxus or in later Greek mathematicians: after being introduced it slowly gave way to the proportion which it is easy to picture as a characteristic of four line segments formed by two parallel lines intersecting the sides of an angle.
The concept of the relation of quantities is a linguistic construct, and quite a complex one. But Platonism did not permit the introduction of constructs in mathematics: it limited the basic concepts of mathematics to precisely representable static spatial images. Even fractions were considered somehow irregular by the Platonic school from the point of view of real mathematics. In The Republic we read: "If you want to divide a unit. learned mathematicians will laugh at you and will not permit you to do it: if you change a unit for small pieces of money they believe it has been turned into a set and are careful to avoid viewing the unit as consisting of parts rather than as a whole.'' With such an attitude toward rational numbers, why even talk about irrational ones!
We can briefly summarize the influence of Platonic idealism on Greek mathematics as follows. By recognizing mathematical statements as objects to work with. the Greeks made a metasystem transition of enormous importance but then they immediately objectivized the basic elements of mathematical statements and began to view them as part of a nonlinguistic reality, "the world of ideas." In this way they closed off the path to further escalation of critical thinking to becoming aware of the basic elements (concepts) of mathematics as phenomema of language and to creating increasingly more complex mathematical constructs. The development of mathematics in Europe was a continuous liberation from the fetters of Platonism."