How do you solve #9=7z-13z-21#?

2 Answers

Answer:

#z=-5#

Explanation:

You combine #7z# and #-13z# to get #-6z#, so

#9=-6z-21#

Add #21# to both sides

#30=-6z#

Divide both sides by #-6#

#-5=z#

Apr 15, 2018

Answer:

#z = -5#

Explanation:

When solving equations, we can combine like terms as shown below:

#5x + 4x -> 9x#

So to solve this problem, we need to isolate the variable "#z#"
We do this by combining all terms with the variable #z# on them.

#9 = 7z - 13z - 21#

#9 = -6z - 21#

Then we treat it as a regular algebra problem by isolating the variable

#9 = -6z - 21#

#30 = -6z#

#z = -5#

Note: Combining like terms can only be done with variables of the same degree, or in other words, variables raised to the same exponent. Example below:

#5z + 3z^2# cannot be combined into one expression, but

#3z^2 + 5z^2# can be combined to produce #8z^2#