How do you solve 9=7z-13z-219=7z13z21?

2 Answers

z=-5z=5

Explanation:

You combine 7z7z and -13z13z to get -6z6z, so

9=-6z-219=6z21

Add 2121 to both sides

30=-6z30=6z

Divide both sides by -66

-5=z5=z

Apr 15, 2018

z = -5z=5

Explanation:

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

5x + 4x -> 9x5x+4x9x

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

9 = 7z - 13z - 219=7z13z21

9 = -6z - 219=6z21

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

9 = -6z - 219=6z21

30 = -6z30=6z

z = -5z=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^25z+3z2 cannot be combined into one expression, but

3z^2 + 5z^23z2+5z2 can be combined to produce 8z^28z2