jawabben plisss ya sya minta tolong

a. 5x-9 - 7x+15y = -2x+15y-9
-3x+5y-4 - 5x-3y+7 = -8x+8y-11
5x^2-9xy-4y^2 -(-x)-6xy+3y^2 = 6x^2-3xy-7y^2

maaf kalo salah

a. 5x -9 - 7x + 15y = 5x -7x. +15y -9 = -2x + 15y - 9
b. 5y - 3x -4 -( 5x - 3y +7) = 5y -3x -4 - 5x +3y -7 = 5y +3y -3x -5x -4-7= 8y -8x -11
c. 5x^2 -9xy -4y^2 -(- x^2 -6xy +3y^2)
= 5x^2 -9xy - 4y^2 + x^2 + 6xy - 3y^2
= 5x^2 +x^2 -4y^2 -3y^2 -9xy +6xy
= 6x^2 - 7y^2 - 3xy