m2_6m+7=0

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Assumption #1, you mean
m^2 - 6m + 7 = 0

Assumption #2, you want to solve this.

it does not factor: so use the formula ...
m = (6 ± √(36 - 4(1)(7) ) )/2
= (6 ± √8)/2
= (6 ± 2√2)/2
= 3 ± √2