Arthur D. answered 11/24/16
Tutor
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(367)
Forty Year Educator: Classroom, Summer School, Substitute, Tutor
a-√x=1/(a+√x) is true when a=√(x+1)
(a-√x)(a+√x)=1
a2-x=1
a2=x+1
√a2=√(x+1)
a=√(x+1)
in other words, it is true when x is 1 less than the square of a