Question

Help me im from VietNam

Answer 1

Answer:

Step-by-step explanation:

Adding and subtracting expressions:

a) M + (5x² -2xy) = 6x² +9xy - y²

                      M = 6x² + 9xy - y² - (5x² - 2xy)

Remove the parenthesis by mulplying each term of 5x² - 2xy by (-1) as (-1) is outside the parenthesis

                           = 6x² + 9xy - y² - 5x² + 2xy

Combine ( add or subtract) like terms.

                           = 6x² - 5x² + 9xy + 2xy - y²

                           = x² + 11xy - y²

Hint: Like terms have same variable with same power.

Here, like terms are (i) 6x² and (-5x²)  (ii) 9xy and 2xy

b)               (3xy - 4y²) - N = x² - 7xy + 8y²

                   3xy - 4y²       = (x² - 7xy + 8y²) + N

3xy - 4y² - (x² - 7xy + 8y²) = N

3xy - 4y² - x² + 7xy - 8y² = N

3xy + 7xy -4y² - 8y² -x²   = N

          10xy -12y²  - x²     = N

Answer: N =  10xy - 12y² -x²