One of the points of intersection of the curves y=1+3x-2x2 and y= 1x is ( 12, 2 ). Let the area of the region enclosed by these curves be 124(l 5+m)-n e(1+ 5), where l, m, n N. Then l+m+n is equal to
- 30
- 29
- 31
- 32
Answer
(1) 30
Solution
Meet: x(1+3x-2x2)=1 2x3-3x2-x+1=0
(2x-1)(x2-x-1)=0 x= 12, 1 52
[figure]
Area = 1/2 (1+3x-2x2- 1x )dx= [x+ 3x22- 2x33- x ]1/2 , = 1+ 52
2= +1, 3=2 +1: upper value = 7 6+ 56- = 17+7 512-
Lower value = 12+ 38- 112+ 2= 1924+ 2
Area = 34+14 5-1924- (2 )= 124(14 5+15)- (1+ 5)
l=14, m=15, n=1 l+m+n=30
Answer: (1)