7*a 2 7 --- - 4*b - - - 2*b 2 a a
-2.0*b - 4.0*b^2
2 / 2 2\ 3
- 7*a + a*\7*a - 4*a *b / - 2*b*a
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3
a 7*a 2 7 --- - 2*b - 4*b - - 2 a a