hey there it's kaylee today we're going to talk about something that i love equations this is a really exciting part of algebra and something you will continue to use in math
ready lets go
to start lets review what we know about algebra so far we know that there are things called expressions an easy one would be 3 plus 4
we can evaluate expressions by order of operations so in this case all we have to do is add and we would get 7 and we
know that expressions can have variables what's a variable again ya it's a number that can vary a number that can change we represent this varying
number as a symbol typically a lower case letter like x so we can have an expression with a variable that looks
like 2 x plus 1 and if we want to evaluate this expression ya we need to know some given values for x
so what if we're told that x is equal to 2 we could evaluate this by using substitution we plug in the given value of 2 wherever we see x so we would get 2
times 2 plus 1 order of operations we multiply first we get 4 plus 1 an that would give us 5 but what if we're told that x is
equal to 6 then to evaluate this expression here we're going to use substitution again so we'll have 2 times 6 plus 1 using order of operations we multiply
first we get 12 plus 1 and that would give us 13 perfect so we know all about expressions that means it won't be too tricky when i tell you what an equation is
an equation is just one expression that is equal to or equates to hence the name equation another expression for example 2x
plus 1 equals 7 is an equation how come because we have an expression on one side 2x plus 1
that's an expression is equal to that's what the equal sign means another expression 7 and yes 7 by itself is an expression
we can have even more complex expressions too like 2x plus y equals 5z
that's an equation because one expression is equal to another expression so what are some equations you
already know some super famous equations are the area of a rectangle do you remember it it says a equals
l times w or area equals length times width how about the circumference of a circle that equation looks like c
equals 2 pie r which means circumference equals 2 times pie times the radius of the circle see that's awesome you already know how to
use equations this isn't so complicated lets do a few examples together where we say if the statement is an equation or an expression this one says
25 minus 4y is this an expression or an equation what do you think well i have
an expression right here and that's it right no equal sign so this one is an expression next one says 3x
plus 2 equals 5 expression or equation well lets see here i have an expression right here equal to another expression remember a number by itself
is an expression so expression equal to expression that means equation perfect and lets do one more last one says
x plus 2y minus z equals 0 expression or equation oof this ones tricky right what does this 0 mean here mean is that an expression
you know what 0 by itself is an expression so that means this equal sign right here that gives it away this one is an equation now that you've been introduced to equations you
can do some practice identifying expressions and equations on your own have fun and remember to always be clever