Student Support Forum > General > > "Numerical analysis gives wrong result"

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 Original Message (ID '201791') By yehuda: I took few more minutes to look at your post there is enough information there to look at 1. You mix exact numbers (integers) with machine precision numbers. One way to get more accurate results is to use rationals or determine the precision of the estimated numbers yourself 2. Using FindRoot is both fast and accurate d1 = -((9.31323*10^-10 (-64. + R)^7 (3. + (-1 + 2.32831*10^-10 (-64. + R)^8) (80. + R)))/(-1 + 2.32831*10^-10 (-64. + R)^8)^2) + (-1 + 2.32831*10^-10 (-64. + R)^8 + 1.86265*10^-9 (-64. + R)^7 (80. + R))/(2 (-1 + 2.32831*10^-10 (-64. + R)^8)); d2=D[d1,R]; sol=FindRoot[d1==0,{R,70,64,80}] returns {R -> 77.6988} so {d1,d2}/.sol returning {0., -0.492557} meets your requirements yehuda