Who gave the general formula to solve quadratic equations?

Examine whether the following equation is quadratic or not: $(3x - 4)^2 - (2x - 3)^2 = 7$.

Solve the following equation using the method of factorization and write its solution set: $\frac{x}{x-1} + \frac{x-1}{x} = \frac{25}{12}$

The formula to find the sum $S$ of the first $n$ natural numbers is $S = \frac{n(n+1)}{2}$. Find $n$ if the sum of the first $n$ natural numbers is $300$.

If the radius of a sphere is doubled,its volume becomes $\ldots \ldots \ldots \ldots$ times the original volume.

The length of a rectangle is $2\,cm$ less than $3$ times its breadth. If its area is $280\,cm^2$,then find its length.