## Substitution

There are two types of substitution.1. Given an equation and some values of different quantities, we can substitute the values of those quantities into the equation.

Example:

\[v=3z^2-2(x+y)\]

. If \[x=4, \: y=1, \: z=2\]

then \[v=3z^2-2(x+y)=3 \times 2^2-2(4+1)=2\]

3. We can substitute equations into other equations. Let

\[a=b^2++2cd\]

and \[c=b+d\]

then we can substitute the second of these into the first.\[a=b^2++2cd=b^2++2(b+d)d=b^2+2bd+2d^2\]