[tex] {7a}^{2} - 3ab + {5b}^{2} - ( - {4a}^{2} - 2ab + {9b}^{2}) \\ = {7a}^{2} - 3ab + {5b}^{2} + {4a}^{2} + 2ab + - {9b}^{2}) \\ = {7a}^{2} + {4a}^{2} - 3ab + 2ab + {5b}^{2} - {9b}^{2}) \\ = {11a}^{2} - ab - {4b}^{2} [/tex]
Answer:
[tex]{11a}^{2} - ab - {4b}^{2} [/tex]
Hope you could understand.
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