derajat suku banyak dan koefisien x4

nggak ngulang soal... langsung masuk ke kali silang...
[tex] = {6x}^{7} - 4 {x}^{5} - 2 {x}^{4} + 4 {x}^{3} - 6 {x}^{6} + 4 {x}^{4} + 2 {x}^{3} - 4 {x}^{2} + 12 {x}^{4} - 8 {x}^{2} - 4x + 8 \\ = 6 {x}^{7} - 6 {x}^{6} - 4{x}^{5} + 14 {x}^{4} +6 {x}^{3} - 12 {x}^{2} - 4x + 8[/tex]
jawaban C.