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The roots of the quadratic function y = 1 / 2 x 2 − 3x + 5 / 2 are the places where the graph intersects the x-axis, the values x = 1 and x = 5. They can be found via the quadratic formula. In elementary algebra, the quadratic formula is a closed-form expression describing the solutions of a quadratic equation.
In number theory, the radical of a positive integer n is defined as the product of the distinct prime numbers dividing n. Each prime factor of n occurs exactly once as a factor of this product: r a d ( n ) = ∏ p ∣ n p prime p {\displaystyle \displaystyle \mathrm {rad} (n)=\prod _{\scriptstyle p\mid n \atop p{\text{ prime}}}p}
Replace x by the average (x + a/x) / 2 between x and a/x. Repeat from step 2, using this average as the new value of x. That is, if an arbitrary guess for is x 0, and x n + 1 = (x n + a/x n) / 2, then each x n is an approximation of which is better for large n than for small n.
The symbol was first seen in print without the vinculum (the horizontal "bar" over the numbers inside the radical symbol) in the year 1525 in Die Coss by Christoff Rudolff, a German mathematician. In 1637 Descartes was the first to unite the German radical sign √ with the vinculum to create the radical symbol in common use today. [3]
If we solve this equation, we find that x = 2. More generally, we find that + + + + is the positive real root of the equation x 3 − x − n = 0 for all n > 0. For n = 1, this root is the plastic ratio ρ, approximately equal to 1.3247.
An unresolved root, especially one using the radical symbol, is sometimes referred to as a surd [2] or a radical. [3] Any expression containing a radical, whether it is a square root, a cube root, or a higher root, is called a radical expression , and if it contains no transcendental functions or transcendental numbers it is called an algebraic ...
In 628, the Indian mathematician Brahmagupta wrote Brāhmasphuṭasiddhānta, which includes, among many other things, a study of equations of the form x 2 − ny 2 = c. He considered what is now called Pell's equation, x 2 − ny 2 = 1, and found a method for its solution. [4] In Europe this problem was studied by Brouncker, Euler and Lagrange.
The numbers and are algebraic since they are roots of polynomials x 2 − 2 and 8x 3 − 3, respectively. The golden ratio φ is algebraic since it is a root of the polynomial x 2 − x − 1. The numbers π and e are not algebraic numbers (see the Lindemann–Weierstrass theorem). [3]