SUBST

Syntax

SUBST ( expression | equation , equation | equation list )

Implemented in iMath since version 2.2.0 or earlier.

Explanation

Substitute the equation or the list of equations into the expression/equation. All substitutions will be done in parallel, which means that after substituting a list of equations like x = y; y = z the expression might still contain the variable y. In this case you need to use SUBSTC instead.

Example

@eq:cubic@ EQDEF x^3 + a x^2 + b x + c = 0

@eq:tsch3@ EQDEF y = x + {a over 3}

EQDEF COLLECT(SIMPLIFY(SUBSTC(@eq:cubic@, SOLVE(@eq:tsch3@, x, 1)),"expand"), y)

This will perform the Tschirnhaus transformation on the cubic equation, reducing it to the depressed form y^3 + p y + q.

See also

SUBSTC SUBSTV SUBSTVC