Let f : R R be a function defined by f(x)= 4x4x+2 and M= f(a)f(1-a)x 4(x(1-x))dx, N= f(a)f(1-a) 4(x(1-x))dx; a 12. If M= N, , N, then the least value of 2+ 2 is equal to .
Answer
5
Solution
f(1-a)= 44+2 4a= 24a+2 ⇒ f(a)+f(1-a)=1
limits add to 1, use x 1-x (integrand 4(x(1-x)) unchanged):
M= f(a)f(1-a)(1-x) 4(x(1-x))dx=N-M
2M=N ⇒ =2, =1 (least natural numbers)
2+ 2=4+1=5
Answer: 5