A positive number exceed its positive square root by 30. Find the number.
According to the question,
$$(x-30)=√x$$ (where x is the positive number).
by taking square on both side,
$$(x-30)^2=(√x)^2$$
or,$$(x^2-60x+900)=x$$
or,$$(x^2-61x+900)=0$$
or,$$(x^2-25x-36x+900)=0$$
So,$$(x-25)(x-36)=0$$
or,$$x=25 and x=36$$
if $$x=25$$ then $$(25-30)=-5$$
but $$√25=5$$ which signifies that -5 is not equal to 5.
So,25 is not that number.
36 is the required number.
So,B is correct choice.
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