If y= -1 ( 3 x-4 x4 x+3 x )+2 -1 ( x1+ 1-x2 ), then dydx at x= 32 is equal to :
- 3
- -1
- 1
- 2
Answer
(3) 1
Solution
In the first term, dividing by 4 x gives 3 x - 4 x4 x + 3 x = 34 - x1 + 34 x = ( - x), where = 34.
Near x = 32, - x (- 2, 2 ), so -1 ( - x) = - x and its derivative is -1.
In the second term put x = , [- 2, 2 ]; then 1 + = 2, so 2 -1 ( 2 ) = = -1x, whose derivative is 1 1 - x2.
dydx = -1 + 1 1 - x2
At x = 32, 1 - 34 = 12, so
∴ dydx = -1 + 2 = 1
Answer: (3)