3a (a + b + c) − 2b (a − b + c)

= 3a^{2} +3ab + 3ac − 2ba + 2b^{2} − 2bc

= 3a^{2 }+ 2b^{2} + ab + 3ac − 2bc

4c (− a + b + c) = − 4ac + 4bc + 4c^{2}

Subtracting these expressions, we obtain

Therefore, the result is −3a^{2} −2b^{2 }+ 4c^{2} − ab + 6bc − 7ac.