《婆羅摩曆算書》中有四章半講嘅係純數學，第12章講嘅係演算系列同少少幾何學。第18章係關於代數，婆羅摩笈多响呢度引入咗一個解二次丟番圖方程例如nx² + 1 = y²嘅方法。
當中方程 嘅解係 ，而色係指常數項c同e。佢然後進一步畀咗二次方程兩個解：
婆羅摩笈多嘅定義唔實用，例如佢覺得 。而佢並無保證 且 嘅講法係啱嘅。
- 內文： 婆羅摩笈多公式
設一個圓內接四邊形嘅四條邊係p﹑q﹑r﹑s，大約面積係 ，設 ，準確面積就係 。
- 英文原文係：“18.44. Diminish by the middle [number] the square-root of the rupas multiplied by four times the square and increased by the square of the middle [number]; divide the remainder by twice the square. [The result is] the middle [number].”
- 英文原文係：“18.45. Whatever is the square-root of the rupas multiplied by the square [and] increased by the square of half the unknown, diminish that by half the unknown [and] divide [the remainder] by its square. [The result is] the unknown.”
- 英文原文係：“12.20. The sum of the squares is that [sum] multiplied by twice the [number of] step[s] increased by one [and] divided by three. The sum of the cubes is the square of that [sum] Piles of these with identical balls [can also be computed]”
- 英文原文係：“18.30. [The sum] of two positives is positives, of two negatives negative; of a positive and a negative [the sum] is their difference; if they are equal it is zero. The sum of a negative and zero is negative, [that] of a positive and zero positive, [and that] of two zeros zero. [...]”
- 英文原文係：“18.32. A negative minus zero is negative, a positive [minus zero] positive; zero [minus zero] is zero. When a positive is to be subtracted from a negative or a negative from a positive, then it is to be added [...]”
- 英文原文係：“18.33. The product of a negative and a positive is negative, of two negatives positive, and of positives positive; the product of zero and a negative, of zero and a positive, or of two zeros is zero.”
- 英文原文係：“18.34. A positive divided by a positive or a negative divided by a negative is positive; a zero divided by a zero is zero; a positive divided by a negative is negative; a negative divided by a positive is [also] negative.”
- 英文原文係：“18.35. A negative or a positive divided by zero has that [zero] as its divisor, or zero divided by a negative or a positive [has that negative or positive as its divisor]. The square of a negative or of a positive is positive; [the square] of zero is zero. That of which [the square] is the square is [its] square-root.”
- 英文原文係：“12.21. The approximate area is the product of the halves of the sums of the sides and opposite sides of a triangle and a quadrilateral. The accurate [area] is the square root from the product of the halves of the sums of the sides diminished by [each] side of the quadrilateral.”
- 英文原文係：“12.40. The diameter and the square of the radius [each] multiplied by 3 are [respectively] the practical circumference and the area [of a circle]. The accurate [values] are the square-roots from the squares of those two multiplied by ten.”
- Seturo Ikeyama (2003). Brāhmasphuṭasiddhānta (CH. 21) of Brahmagupta with Commentary of Pṛthūdhaka, critically edited with English translation and notes. INSA.
- "Brahmagupta biography". School of Mathematics and Statistics University of St Andrews, Scotland. 喺2013-07-15搵到.
- David Pingree. Census of the Exact Sciences in Sanskrit (CESS). American Philosophical Society. pp. p254.CS1 maint: extra text (link)
- Boyer (1991). "The Arabic Hegemony". p. 226.
By 766 we learn that an astronomical-mathematical work, known to the Arabs as the Sindhind, was brought to Baghdad from India. It is generally thought that this was the Brahmasphuta Siddhanta, although it may have been the Surya Siddhanata. A few years later, perhaps about 775, this Siddhanata was translated into Arabic, and it was not long afterwards (ca. 780) that Ptolemy's astrological Tetrabiblos was translated into Arabic from the Greek.Missing or empty
- Boyer (1991). "China and India". p. 220.
However, here again Brahmagupta spoiled matters somewhat by asserting that , and on the touchy matter of , he did not commit himself:Missing or empty
- Template:Harv Brahmagupta does not explicitly state that he is discussing only figures inscribed in circles, but it is implied by these rules for computing their circumradius.
- "Brahmagupta, and the influence on Arabia". School of Mathematical and Computational Sciences University of St Andrews. 2002-05. 喺2013-07-15搵到. Check date values in: