Question

Find the roots of x^2-9x+20=0

Answer 1

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Answer 2

Given Equation is x^2 - 9x + 20 = 0

Here a = 1, b = -9, c = 20.

We know that x = $\frac{-b + \sqrt{b^2-4ac} }{2a}$

                           = $\frac{-(-9) + \sqrt{(-9)^2 - 4 * 1 * (20)} }{2}$

                           = $\frac{9+ \sqrt{81 - 80} }{2}$

                           = $\frac{9 + 1}{2}$

                          = $\frac{10}{2}$

                          = 5.



We know that x = $\frac{ - b - \sqrt{b^2 - 4 * a * c} }{2a}$

                           = $\frac{-(-9) - \sqrt{(-9)^2 - 4 * 1 * 20 } }{2 * 1}$

                           = $\frac{9 - \sqrt{81 - 80} }{2}$

                          = $\frac{9 - 1}{2}$

                          = $\frac{8}{2}$

                          = 4.


Therefore the roots of the equation is  5 and 4.


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