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Index
An index is a symbol often placed to the right and below another symbol, which it characterizes or numbers.
Explanation
In the notation x1, the 1 is the index of x, which reads x one.
Example 1
You can factorize the quadratic function f (x) = ax2 + bx + c using the quadratic formula
and with the Viète formulas you can write the sum and the product of the roots as
and
Example 2
In a polynomial of degree n
P(x) = anxn + an−1xn−1 + ··· + a2x2 + a1x + a0 = (x − x1)(x − x2) ··· (x − xn)
are x1, x2, ... , xn the zeroes and are a0, a1, a2, ... , an the coefficients of the different terms.