Answer:
The side length is multiplied by 
Step-by-step explanation:
we know that
The area of the original square is equal to

If the area is doubled
then
The area of the larger square is

Remember that
If two figures are similar, then the ratio of its areas is equal to the scale factor squared
Let
z ----> the scale factor
x ----> the area of the larger square
y ---> the area of the original square
so

we have




------> scale factor
therefore
The side length is multiplied by 