Let f(x)= ( 16x+24x2+2x-15 )dx. If f(4)=14 e(3) and f(7)= e (2 3 ), , N, then + is equal to :
- 31
- 37
- 39
- 41
Answer
(3) 39
Solution
x2+2x-15=(x+5)(x-3)
16x+24(x+5)(x-3)= Ax+5+ Bx-3
x=3: 72=8B B=9; x=-5: -56=-8A A=7
f(x)=7 e|x+5|+9 e|x-3|+C
f(4)=7 e 9+9 e 1+C=14 e 3+C=14 e 3 C=0
f(7)=7 e 12+9 e 4= e (214 37 218 )= e (232 37 )
=32, =7
+ =39
Answer: (3)