fix c++ code and displayed precision

[fdiblen]

• Fix tolerance comparison in c++ code
• Use 6 decimal point precision for output
• Display initial values of guess variable and tolerance.

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
0.0% Duplication