Answer:
x=20
Explanation:
Right angle triangle ABC
ac^2=ab^2+bc^2
or (x+9)^2=x^2+(x+1)^2
or x^2+81+18x=x^2+x^2+1+2x
or 80= X^2-16x
or x^2-16x-80=0
x^2-20x+4x-80=0
x(x-20)+4(x-20)=0
(x+4)(x-20)=0
either x=-4 or x=20
since x is a length it can not be negative