Direct substitution

example:

Dividing out

example:

direct substitution would not work here because when you but -3 in for x the denominator will equal zero.

to use dividing out you would first factor

(x+3) will cancel out

now use Direct Substitution

Rationalizing

example:

if you use direct substitution...

first you have to rationalize the sqrt

X cancels out

now use direct substitution