《婆罗摩历算书》中有四章半讲个是纯数学，第12章讲个是演算系列搭少许几何学。第18章是关於代数，婆羅摩笈多在昰𡍲引入仔一個解二次丟番圖方程像nx² + 1 = y²个方法。
當中方程 个解是 ，而色是指常數項c搭e。佢然後進一步給了二次方程兩隻解：
昰𡍲婆羅摩笈多所畀个頭 個自然數个平方搭立方个算法，分別爲 搭
婆羅摩笈多个定義弗實用，比方佢認爲 。而佢並嘸沒保證 且 个說法是對个。
設一個圓內接四邊形个四條邊爲p﹑q﹑r﹑s，大約面積爲 ，設 ，準確面積嚜爲 。
- 英文原文是：“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].”
- 英文原文是：“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.”
- 英文原文是：“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]”
- 英文原文是：“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. [...]”
- 英文原文是：“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 [...]”
- 英文原文是：“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.”
- 英文原文是：“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.”
- 英文原文是：“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.”
- 英文原文是：“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.”
- 英文原文是：“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. 访问日脚2013-07-15.
- David Pingree．Census of the Exact Sciences in Sanskrit (CESS)．American Philosophical Society，p254．
- 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). 访问日脚2013-07-15.