To add or subtract terms with exponents, both the base and the exponent must be the same. In this case they are so subtract the coefficients and retain the base and exponent:

4z² - 9z²
(4 - 9)z²
-5z²

The distributive property for multiplication helps in solving expressions like a(b + c). It specifies that the result of multiplying one number by the sum or difference of two numbers can be obtained by multiplying each number individually and then totaling the results: a(b + c) = ab + ac. For example, 4(10-5) = (4 x 10) - (4 x 5) = 40 - 20 = 20.

A rational number (or fraction) is represented as a ratio between two integers, a and b, and has the form \({a \over b}\) where a is the numerator and b is the denominator. An improper fraction (\({5 \over 3} \)) has a numerator with a greater absolute value than the denominator and can be converted into a mixed number (\(1 {2 \over 3} \)) which has a whole number part and a fractional part.

The least common multiple (LCM) is the smallest positive integer that is a multiple of two or more integers.

Use PEMDAS (Parentheses, Exponents, Multipy/Divide, Add/Subtract):

2 + (4 + 2) ÷ 5 x 4 - 5²
P: 2 + (6) ÷ 5 x 4 - 5²
E: 2 + 6 ÷ 5 x 4 - 25
MD: 2 + \( \frac{6}{5} \) x 4 - 25
MD: 2 + \( \frac{24}{5} \) - 25
AS: \( \frac{10}{5} \) + \( \frac{24}{5} \) - 25
AS: \( \frac{34}{5} \) - 25
AS: \( \frac{34 - 125}{5} \)
\( \frac{-91}{5} \)
-18\(\frac{1}{5}\)