Let's first simplify the expression step by step:
(7-6c)(6c+7c) = (7-6c)(13c) = 7(13c) - 6c(13c) = 91c - 78c^2
-9c(2-4c) = -9c(2) - (-9c)(4c) = -18c + 36c^2
Putting it all together:
(7-6c)(6c+7c) - 9c(2-4c) - 49 = 91c - 78c^2 - 18c + 36c^2 - 49
Combining like terms:
91c - 78c^2 - 18c + 36c^2 - 49= 91c - 18c - 78c^2 + 36c^2 - 49= 73c - 42c^2 - 49
Therefore, the simplified expression is 73c - 42c^2 - 49.
Let's first simplify the expression step by step:
(7-6c)(6c+7c) = (7-6c)(13c) = 7(13c) - 6c(13c) = 91c - 78c^2
-9c(2-4c) = -9c(2) - (-9c)(4c) = -18c + 36c^2
Putting it all together:
(7-6c)(6c+7c) - 9c(2-4c) - 49 = 91c - 78c^2 - 18c + 36c^2 - 49
Combining like terms:
91c - 78c^2 - 18c + 36c^2 - 49
= 91c - 18c - 78c^2 + 36c^2 - 49
= 73c - 42c^2 - 49
Therefore, the simplified expression is 73c - 42c^2 - 49.