Download Evaluating Expressions

Evaluating Expressions
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What do you use when substituting a value?
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What does evaluate mean?
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What does substitute mean?
What is a variable?
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Give some examples of variables.
What is a constant?
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What is a coefficient?
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When substituting -3 for x into x², how
would we write it? Where does the
exponent go?
What is a term?
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What separates one term from another?
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In the expression  6 x 2  2 x  3 y  4 what
are the constants and the coefficients?
Describe the difference between an
expression and an equation.
What is the proper way to write an x times
3?
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Parentheses Ex: 2x+4 when x = 3
Calc: 2(3)+4
Plug in number and find numerical answer
(solve)
Plug in something
A letter or symbol that represents a number
(emphasize this!!!)
Various answers x, y, r, , <3 ….
A constant is a number by itself with no
variable. The value of this term never changes,
ie: remains CONSTANT (the SAME)
A coefficient is a number in front of a
variable. The coefficient is being multiplied
with the variable
With parentheses. The exponent goes outside
(-3)2
A number or variable or a coefficient with a
variable. Terms do NOT have + or + or - Ex: 3x – 4 +7yz has 3 terms. (draw lines
where you see the – and +
Constant: -4 (NOT 4!!!!)
Coefficients: -6, -2 and 3 (NOT 6 and 2!!!)
An equation has an equal sign and an
expression does not.
3x: the number (coefficient) goes in the
front. If they just say “number” ask: What is
this number called when it is in front of a
variable? Coefficient
Four.
How many terms does the expression
 6 x 2  2 x  3 y  4 have?
How can we determine the number of terms? Separate the terms with the + and – signs.
What is the difference between a constant
A constant term does not have a variable. The
and a coefficient?
value of this term never changes. A coefficient
has a variable next to it. The value of this term
can change. 2x: if x = 3 then the value is 6, if x
= 10, the value is 20.
If the variable is alone (ex: x), does it have a YES. There is always a coefficient of invisible
coefficient? (If yes, what is it?)
1. If there was not any x’s (zero) then why
would we write it? For ex x+ 3x = 4x b/c
1x+3x: 1+3=4. if there were only 3, why would
we even write the “x” term?
Give an example of an Algebraic Expression Algebraic : various answers; must have
and a numerical expression. Be able to
variables (no equal sign)
explain the difference.
Numerical: various answers; cannot have
variables (no equal sign)
Algebraic expressions have variables,
numbers and operation symbols. Numerical
expressions only have numbers and operation
symbols.
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Lead in:
What is different about algebra vs “old/8th
grade” math?
So what do we think ALGEBRAIC
expressions have different than numerical
expressions?
What is an example of something you would
have done in 8th grade? (or earlier) What
does this have?
Now if we want to make it ALGEBRAIC,
what would we change?
How would you read/say 3( x  2) ?
What is the proper way to write the sum of a
number and a variable term? (ex. 4
increased by 2x)
Algebra has variables
Variables
A numerical expression: 3+4
Numbers and symbol (plus sign)
Put in variables: 3x+4x
“Three times the QUANTITY x minus 2”
2x+4. The variable term should go FIRST.
Explain that it is not wrong to write 4+2x, but it
is “improper,” Just like it is not “wrong if we
write “juan”(its still the same name) but it is
“improper.” Also 2x+4 is how students will see
it on tests so they need to get used to the
“proper” way of writing algebra.