I have to use 4 digit arithmetic and rounding to get the relative error of a calculation and then manipulate the expression in order to reduce the error. Here is the calculation:
Finding roots of $f(x) = x^2 + 90x - 1$
I can’t get to the manipulating part where the error of the root close to zero is essentially supposed to reduce from 9.99% to near 0%
For a quadratic equation $x^2+a x+b=0$ the roots are given by $$x_\pm=\frac 12 \left(-a \pm \sqrt{a^2-4b} \right)$$ but you can rewrite them (multiply by the conjugate) $$x_\pm=-\frac {2b}{a \pm \sqrt{a^2-4b}}$$ This is a good practice when coding if $b \ll a^2$