Question

5.From 6x^2-7xy+8y^2 subtract the sum of x^2−3xy−y^2and 2x^2+5xy−4y^2

Answer 1

6x^2 - 7xy + 8y^2 - (x^2 - 3xy - y^2 + 2x^2 + 5xy -4y^2) 
6x^2 - 7xy + 8y^2 - (3x^2 + 2xy - 5y^2)
6x^2 - 7xy + 8y^2 - 3x^2 - 2xy + 5y^2
3x^2 - 9xy +13y^2