subtract (2x² - 3xy + 7y²) from (5x² - 8xy + y²) and (7x + xy - 5)

Question

please tell me how to do questions like this

Answer 1

5x²-8xy+y²-(2x²-3xy+7y²) is the way to write the question.

The next step is to apply distribution of the negative outside the bracketed expression. The minus sign switches all the signs within this expression:

5x²-8xy+y²-2x²+3xy-7y².

Next, look for similar terms and group them:

5x²-2x² - 8xy+3xy +y²-7y².

Now perform arithmetic in these groups:

3x² - 5xy - 6y² which is the answer for this subtraction.

7x+xy-5-(2x²-3xy+7y²).

Note that xy is the only common term in the expressions.

7x+xy-5-2x²+3xy-7y²,

7x + xy+3xy -5-2x²-7y²,

7x+4xy -5-2x²-7y². This look untidy so rearrange the terms by degree (greatest first):

-2x²+4xy-7y²+7x-5 is tidier. The degree is obtained by adding the exponents of variables in each term.

x² has degree 2, as do xy and y² so these come first. x has degree 1 and there's only one term, that is, 7x. The constant has degree 0 so comes last.