1. State the values of $a$ and $b$ from part (a) and write the expression for $g(x)$
From part (a), a=−14 and b=22.
f(x)=2x3−14x2+22x−10
g(x)=2x3−14x2+22x−10+k
2. Apply the Factor Theorem to find $k$
Since g(x) is divisible by 2x−1, by the Factor Theorem, g(21)=0.
2(21)3−14(21)2+22(21)−10+k=0
2(81)−14(41)+11−10+k=0
41−27+1+k=0
0.25−3.5+1+k=0
−2.25+k=0
k=2.25