I need help simple explanation if possible

Answer:
In a 45°−45°−90° triangle, the length of the hypotenuse is 2√‾ times the length of a leg. Note that an isosceles right triangle must be a 45°−45°−90° triangle. x2+x2=2x2=(x2‾√)2
i know this isn't an easy explanation but hopefully it might clear something up for you? ill keep looking for things just in case..
Answer:
x = 7
Step-by-step explanation:
use pythagoras theorem
x² + ײ = (7.sqrt(2))²
2x² = 49x2
x² = 49
× = 7