reemember
a²+b²=c²
for a right traingle where a and b are legs and c is hyptoonuse
given
a=x-2
b=x
c=√20
(x-2)²+(x)²=(√20)²
x²-4x+4+x²=20
2x²-4x+4=20
divide both sides by 2
x²-2x+2=10
minus 10 both sides
x²-2x-8=0
factor
what 2 numbers multily to get -8 and add to get -2
-4 and 2
(x-4)(x+2)=0
set to zero
x-4=0
x=4
x+2=0
x=-2, false we can't get negative measures
x=4
B is answer
