Innocent looking expression does not simplify

[jw3126]

The following should be zero:

using SymbolicUtils

@syms a1::Real a2::Real B12::Real B13::Real B23::Real


zero1 = a1*( B12+ 1)*a2 +
        a2*(-B12*a1 - a1)

@show zero1
@show simplify(zero1)

zero1 = a2*(-a1 - (B12*a1)) + a1*a2*(1 + B12)
simplify(zero1) = a2*(-a1 - (B12*a1)) + a1*a2*(1 + B12)

[david-pl]

Try simplify(zero1,expand=true).

[jw3126]

Thanks @david-pl this works for me! Do you know why expand=false is the default?

[david-pl]

Not in detail, but IIUC using expand=true can be computationally expensive so it should only be used when needed. Hence the default expand=false.