From Wikipedia[1]: "In the 9th and 10th century AD, Islamic mathematicians were familiar with negative numbers from the works of Indian mathematicians, but the

From Wikipedia[1]: "In the 9th and 10th century AD, Islamic mathematicians were familiar with negative numbers from the works of Indian mathematicians, but the recognition and use of negative numbers during this period remained timid. Al-Khwarizmi in his Al-jabr wa'l-muqabala (from which we get the word "algebra") did not use negative numbers or negative coefficients, although al-Karaji wrote in his al-Fakhrī that "negative quantities must be counted as terms"." So it would indeed seem that your interpretation is what al-Khwarizmi meant. [1] http://en.wikipedia.org/wiki/Negative_number#History http://en.wikipedia.org/wiki/Negative_number#History