Answer
a. $10000-x^2$
b. Area of te original is $10000$ and the area is decreased by $x^2$
c. $9559$
Work Step by Step
a. $(100-x)(100+x)=100^2-x^2=10000-x^2$
b. Area of te original is $10000$ and the area is decreased by $x^2$
c. $10000-x^2, x=21$ $=10000-441=9559$
