The Flip command flips the limits of integration of v: ${\int }_a^{b}f\left(x\right)\ⅆx=-\left({\int }_b^{a}f\left(x\right)\ⅆx\right)$.

$\mathrm{with}\left(\mathrm{IntegrationTools}\right)\:$

$v≔\mathrm{Int}\left(f\left(x\right)\,x=a..b\right)$

$v≔{\int }_a^{b}f\left(x\right)\ⅆx$

$\mathrm{Flip}\left(v\right)$

$-\left({\int }_b^{a}f\left(x\right)\ⅆx\right)$