I have the following expression:
eqs3=-2.750863054772633*^7*Subscript[x, 18] + 197943.17573209677*Sqrt[1.03*^7 - 1.*Subscript[x, 19]] +
2.750863054772633*^7*Subscript[x, 19] +
(-95931.14816252001 + (1.2622519495068421*^9*
(-0.0001568174846625767*Sqrt[1.03*^7 - 1.*Subscript[x, 18]] + 0.021793296146996537*
Subscript[x, 18] + 0.000076*Sqrt[1.03*^7 + Subscript[x, 18]] -
0.021793296146996537*Subscript[x, 19]))/Sqrt[1.03*^7 + Subscript[x, 18]])*
Sqrt[1.03*^7 + Subscript[x, 19]]
I'm going to apply several rules, as follows.
eqs3 /.
Thread[{Subscript[x, 19], Subscript[x, 18]} -> -8673600.700]
(*0*)
eqs3 /.
Thread[{Subscript[x, 18], Subscript[x, 19]} -> -8673600.700]
(*0*)
eqs3 /. Subscript[x, 18] -> -8673600.700 /.
Subscript[x, 19] -> -8673600.700
(*0*)
So far so good, if it wasn't that...
eqs3 /. Subscript[x, 19] -> -8673600.700 /.
Subscript[x, 18] -> -8673600.700
(*0.00842667*)
Why is so??? This is very much disappointing.
eqs3[[8]]
does not make much sense?! $\endgroup$ – gwr Feb 28 '17 at 15:19