book Maths Puzzle Numerical Ability

please help with this problem.

Solve the equation.

x^2 - x = 90

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book Other Question

If two numbers have opposite signs, their quotient is,... Determine whether each relation is a funtion, justify your answer.

{(0,1), (1,0), (2,1), (3,1), (4,2)}

HOw do i solve this problem?