Answer:
When it is divided by x-1 and it has no remainder , then it means substituting x=1 into the polynomial is zero .Because x-1 is a factor.
[tex]2 {x}^{3} - a {x}^{2} - 7x + 6 \\ x = 1 \\ 2 {(1)}^{3} - a {(1)}^{2} - 7(1) + 6 = 0 \\ 2 - a - 7 + 6 = 0 \\ 1 - a = 0 \\ a = 1[/tex]
