What number has the same absolute value as 81?

What is the y-intercept of the line given by the equation

If 2(a^2+b^2)=(a+b)^2 then, > a+b=0, > ab=0, > a=b, > 2a=b

Write each of the following numerals in base 10. for base twelve, t and e represent the face values ten and eleven, respectively. 114 base 5 89t base 12