Combine like terms to simplify the expression.

Start by changing the -2x to plus a negative 2x.

So we have 6x² + 3y² + 4y² - 2x.

Note that 3y² and 4y² are like terms because

they are exactly alike except for their coefficients.

So 3y² + 4y² simplifies to 7y².

Although 6x² and -2x look similar, they are not like terms.

So our final answer is 6x² + 7y² + -2x.

Step-by-step explanation:

It must be 508 students heights, because the problem is asking for a population variance, not a sample variance, which is calculated with a different formula.

Remember that population is the total number of subjects that are being studied, and sample is a subgroup of that total number.