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Status: Waiting for your answers.

Problem: Solve for the variable. Check a value if it is extraneous.   √ f - 5  = f - 7   f - 5 = ( f + )2   f - 5 = f2 + f +   0 = f2 + f +   0 = ( f + )( f + )   f1 =     f2 = extraneous   extraneous