Question

11a square - 5b square + 12c from 15a square + 7b square - 3c​

Answer 1

$(11 {a}^{2} - {5b}^{2} + 12c) + \\ ( {15a}^{2} + 7 {b}^{2} - 3c) \\ = {26a}^{2} + {2b}^{2} + 9c$