Question

x²-2x-1=0 Precizati daca 1-√2 este solutia ecuatiei....?

Answer 1

$Pentru~x=1- \sqrt{2},~avem : \\ \\ x^{2} -2x-1= \\ =(1- \sqrt{2})^{2}-2(1 -\sqrt{2})-1 = \\ =(1-2 \sqrt{2}+2)-2(1- \sqrt{2})-1= \\ =1-2 \sqrt{2}+2-2+ 2\sqrt{2}-1= \\ =0,~deci~1- \sqrt{2}~este~o~solutie~a~ecuatiei~date.$