If the function f:(- ,-1] (a,b] defined by f(x)=ex3-3x+1 is one-one and onto, then the distance of the point P(2b+4,a+2) from the line x+e-3y=4 is :
- 2 1+e6
- 1+e6
- 3 1+e6
- 4 1+e6
Answer
(1) 2 1+e6
Solution
f'(x)=3(x-1)(x+1) ex3-3x+1 0 on (- ,-1] ⇒ f is increasing
x - f(x) 0 and f(-1)=e-1+3+1=e3
∵ onto, range =(0, e3] a=0, b=e3
P (2e3+4, 2 )
d= |2e3+4+2e-3-4 | 1+e-6= 2 (e3+e-3 ) 1+e-6
Multiply above and below by e3: d= 2 (e6+1 ) e6+1=2 1+e6
Answer: (1)