How can I get precise result?

I'm new to Matlab and I did some test.

format longG
a = [1 -1 -1 3; 2 -1 -3 1; 3 2 -5 2; 3 1 2 2]
b = adjoint(a)
a * b

The result looks like this:

As you can see, there are a lot .9999999... and e-14 or e-15. These e-14 or e-15 numbers are actually all 0s. How can I get precise result?

I did a similar calculation in Mathematica, and below is the result.

How can I get this similar result in Matlab? Thanks.

Answer 1

[madhan ravi]

 a * sym(b)

[Ivor Horton]

Thank you! This works. By the way, I have to use sym() from the first calculation in order to get what I want. Should I always use sym() in order to get precise result? Are there any guidelines?

[madhan ravi]

Indeed! https://www.mathworks.com/help/symbolic/sym.html#bu1rs8g-1

[Ivor Horton]

Thanks again!