Since a=5√2,one can substitute 5√2 for a in 2a=√2x,giving 10√2=√2x , Squaring each side of 10√2=√2x gives (10√2)2=(√2x)2, which simplifies to (102)(√2)2=(√2x)2,or 200=2x.The gives x=100. Checking x=100 in the original equation gives 2(5√2)−√(2)(100), which is true since 2(5√2)=10√2 and √(2)(100)=(√2)(√100)=10√2