Question

if a is equal to 7 x square + 5 x y -9 y square b=-4 x square + xy +5y square comma C is equal to 4 y square - 3 x square - 6 x y then show that a + b + C is equal to zero

Answer 1

$7 {x}^{2} + 5xy - 9 {y}^{2} - 4 {x}^{2} + xy + 5 {y}^{2} + 4 {y}^{2} - 3 {x}^{2} - 6xy = 0$

Answer 2

Heres your answer mate

a = {7x}^{2} + 5xy - 9 {y}^{2} \\ \

\ b = - 4 {x}^{2} + xy + 5 {y}^{2} $a = {7x}^{2} + 5xy - 9 {y}^{2} \\ \\ b = - 4 {x}^{2} + xy + 5 {y}^{2} \\ \\ c = 4 {y}^{2} - 3 {x}^{2} - 6xy \\ \\ a + b + c \\ \\ 7 {x}^{2} + 5xy - 9 {y}^{2} + ( - 4 {x}^{2} + xy + 5 {y}^{2} ) + \\ (4 {y}^{2} - 3 {x}^{2} - 6xy) \\ \\ = (7 {x}^{2} - 4 {x}^{2} - 3 {x}^{2} ) - 9 {y}^{2} + 5 {y}^{2} + 4 {y}^{2} + (5xy + xy \\ - 6xy) \\ \\ = 0 {x}^{2} + 0 {y}^{2} + 0xy \\ \\ = 0$
Hence the answer is 0

Hope it Helps!!..