Answer:
7x^2-4x+3y^2 ( the ^ means the exponent EX: 5^2 is 5 squared. )
Explanation:
Remove the parenthesis (a) = a
12x^2-11y^2-13x- (5x^2-14y^2-9x)
-(5x^2 - 14y^2 - 9x)
Distribute parenthesis
-(5x^2) - (14y^2) - (-9x)
Apply minus - plus rules
-5x^2 + 14y^2 + 9x
= 12x^2 - 11y^2 - 13x - 5x^2 + 14y^2 + 9x
Simplify
12x^2-11y^2-13x-5x^2+14y^2+9x
Group like terms
12x^2-5x^2-13x+9x-11y^2+14y^2
Add similar elements
7x^2-13x+9x-11y^2+14y^2
Add similar elements ( - 13x + 9x = -4x )
7x^2-4x-11y^2+14y^2
Add similar elements 11y^2 + 14y^2 = 3y^2
7x^2-4x+3y^2