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الاجناس من الطرفين بعدة واحدة قيل هي تقابل بعض الاشيآء ببعض علي المساوات كما في مثال المذكور اذا قوبلت العشرة بالخمسة علي المساوات وسمي العلم بهذين العلمين ..... علم الجبر والمقابلة لكثرة وقوعها فيه
For instance if we say: ‘Ten less one thing equal to four things;’ then jebr is the removal of the subtraction, which is performed by adding to the minuend an amount equal to the subtrahend: hereby the ten are made complete, that which was defective in them being restored. An amount equal to the subtrahend is then added to the other side of the equation as in the above instance, after the ten have been made complete, one thing must be added to the four things, which thus become five things. Mokābalah consists in withdrawing the same amount from quantities of the same kind on both sides of the equation; or as others say, it is the balancing of certain things against others, so as to equalize them. Thus, in the above example, the ten are balanced against the five with a view to equalize them. This science has therefore been called by the name of these two rules, namely, the rule of jebr or restoration, and of mokābalah or reduction, on account of the frequent use that is made of them.”
3. The following is an extract from a treatise by
Abu Abdallah al-Hosain ben Ahmed,[1] entitled, المقدمة
- ↑ I have not been able to find any information about this writer. The copy of the work to which I refer is comprized in the same volume with Mohammed ben Musa’s work in the Bodleian library. It bears no date.
