8th Variables and Expressions
 To evaluate an expresion means to find itsvalueTo avoid confusion, mathematicians have agreed to a set of          called the order of operations.When you                       a number for the variable, an algebraic expression becomes a numericalexpression.A variable is a               , usually a letter, used torepresent a                .An algebraic expression contains a                   , a number, and at least one                   symbol.substitute?number?symbol?operation?variable?numeric? Evaluate each expression if q = 5, r = 6 and s = 3.  4(r - s)2=4= 4 (    )2= 4 x = (36?6?9?3?-3)2←←←Perform operations in the  first.Evaluate the power.SimplifyReplace  with 6and  with 3.parentheses?s?r? Expressions such a 72 and 23 are called powersand represent repeated Remember q = 5, r = 6 and s = 3.= (  q2 - 4r - 15?===)22525?1?- 4- - 4(6) -1-  1(24?6?)- 1- 1←replace the q with 5replace the r with 6Since you have no parentheses you mustevaluate the exponents firstWork from left to right when operations are the same.
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