Question

If ${\int }_1^a(3x^2+2x+1)dx=11$, find real values of a.

• A. 0
• B. 3
• C. 2
• D. 1

Answer 1

Answer: (C)

2

${\int }_1^a(3x^2+2x+1)dx=11$

$[x^3+x^2+x{]}_1^a=11$

$(a^3+a^2+a)-(1+1+1)=11$

$a^3+a^2+a-14=0$

$(a-2)(a^2+3a+7)=0$

$a=2$