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What is the sum of all values of z such that z^2 = 12z - 7 + 9z - 5?

 Feb 27, 2021
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z^2 -21z+12 = 0        via quadratic formula z =   21/2 ±  sqrt(393) /2

                                                              sum = 42/2 = 21                              (which is just   - b/a)

 Feb 27, 2021
edited by ElectricPavlov  Feb 27, 2021

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