Numeric Substitutions:


Evaluate 2x  3, when x = 4. 


Replace x with 4 and simplify. 


2(4)  3 = 8  3 = 5 Answer


Evaluate x^{2 }  1, when x = 5. 


Replace x with 5 and simplify. 


(5)^{2}  1 = 25  1 = 24 Answer


Evaluate a^{2 }+ a, when a = 3. 



Replace all values of a with 3 and simplify.



(3)^{2} + (3) = 9 + 3 = 12 Answer


Evaluate 6x + 3y, when x = 2 and y = 5. 


Notice the use of two variables. Replace each and simplify. 


6(2) + 3(5) = 12 + 15 = 27 Answer


Evaluate x^{3} + 3x^{2}  2x  5, when x = 4. 


Especially use parentheses when working with negative values. 


(4)^{3} + 3(4)^{2}  2(4)  5 = 64 + 48 + 8  5 = 13 Answer


Evaluate a^{2}b + a, when a = 3 and b = 2. 
Do NOT write:
3^{2}(2) + (3) as this is
9(2) + (3) = 21 



Parentheses are needed in this problem.



(3)^{2}(2) + (3) = 18 + (3) = 15 Answer 
Algebraic Substitutions:
It may be the case that you will be asked to evaluate an expression using another expression.
Don't panic!!! Just follow the same process as you did when evaluating for a number.


Evaluate x^{2} + 2x  4, when x = 2a. 


Remember to use parentheses! 


(2a)^{2} + 2(2a)  4 = 4a^{2} + 4a  4 Answer
