Let f(x)= |2 x2+5|x|-3 |, x R. If m and n denote the number of points where f is not continuous and not differentiable respectively, then m+n is equal to :
- 5
- 3
- 2
- 0
Answer
(2) 3
Solution
2x2+5|x|-3=(2|x|-1)(|x|+3)=0 x= 12
[figure]
f is built from continuous functions continuous everywhere =0
Sharp corners at x=- 12, 0, 12 =3
corner of |x| at 0; 2x2+5|x|-3 changes sign at 12
+n=0+3=3
Answer: (2)