According to the original formula the variance of a random variable X is equal to the expected value of the squared difference between X and its mean. Start with the standard form of a general quadratic equation. We typically stop at n1 n 1 because we usually want n n to equal the total number of terms and we have to include that r0 r 0 This has a well known formula for the sum for a derivation check out Khan Academy.
Complete the square by adding b2 4 a2 to both sides of the equation.
Subtract c displaystyle c from both sides. Y Dy x Dx Dy x Dx y. Derivation of Quadratic Formula 1. Divide both sides by a displaystyle a.