5^x-1 = 10^x 2^-x × 5^x+1

5^x/5=(5^x*2^x)/2^x*5*5^x 5^x/5=5^2x*5 5^x=5^2x*25 5^x=5^(2x+2) x=2x+2 2x-x=-2 x=-2