A= x² + xy +2y-1
a+b= 2x² - xy - 4y-1
a) find a-b
b) if (a-b) = x
find y

see explanation

Step-by-step explanation:

Given the 2 equations

A = x² + xy + 2y - 1 → (1)

A + B = 2x² - xy - 4y - 1 → (2)

From (2)

B = 2x² - xy - 4y - 1 - A

   = 2x² - xy - 4y - 1 - (x² + xy + 2y - 1) ← distribute parenthesis

   = 2x² - xy - 4y - 1 - x² - xy - 2y + 1 ← collect like terms

   = x² - 2xy - 6y

Hence

A - B = x² + xy + 2y - 1 - (x² - 2xy - 6y) ← distribute parenthesis

        = x² + xy + 2y - 1 - x² + 2xy + 6y ← collect like terms

        = 3xy + 8y - 1

(b)

Given A - B = x, then

x = 3xy + 8y - 1 ( add 1 to both sides )

x + 1 = 3xy + 8y ← factor out y from each term

x + 1 = y(3x + 8) ← divide both sides by (3x + 8)

y =