1. Apply the Factor Theorem to form the first equation
Let f(x)=2x3+ax2+bx+10.
Since x+2 is a factor, f(−2)=0.
2(−2)3+a(−2)2+b(−2)+10=0
−16+4a−2b+10=0
4a−2b=6
2a−b=3— (1)
2. Apply the Remainder Theorem to form the second equation
Since the remainder is 10 when divided by x−3, f(3)=10.
2(3)3+a(3)2+b(3)+10=10
54+9a+3b+10=10
9a+3b=−54
3a+b=−18— (2)
3. Solve the simultaneous equations for $a$
Adding equation (1) and equation (2):
(2a−b)+(3a+b)=3+(−18)
5a=−15
a=−3
4. Solve for $b$
Substitute a=−3 into equation (1):
2(−3)−b=3
−6−b=3
b=−9
答案a=−3, b=−9