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If f(x)=x+x5f(x) = |x| + |x - 5|, then which of the following statements are TRUE?

(A) f is a continuous function every where

(B) f is a continuous function except x=5x = 5 and x=0x = 0

(C) f is a continuous function except x=0x = 0 but not differentiable at x=5x = 5

(D) f is a continuous function everywhere but not differentiable at x=0x = 0 and x=5x = 5

Choose the correct answer from the options given below:

Solution

Correct Option: 3

The function f(x)=x+x5f(x) = |x| + |x - 5| changes behavior at x=0x = 0 and x=5x = 5.

For x<0x < 0:

x=x|x| = -x

x5=x+5|x - 5| = -x + 5

f(x)=2x+5f(x) = -2x + 5

For 0x<50 \leq x < 5:

x=x|x| = x

x5=x+5|x - 5| = -x + 5

f(x)=5f(x) = 5

For x5x \geq 5:

x=x|x| = x

x5=x5|x - 5| = x - 5

f(x)=2x5f(x) = 2x - 5


At x=0x = 0:

f(0)=2(0)+5=5f(0^-) = -2(0) + 5 = 5

f(0+)=5f(0^+) = 5

f(0)=5f(0) = 5

The function is continuous at x=0x = 0.

At x=5x = 5:

f(5)=5f(5^-) = 5

f(5+)=2(5)5=5f(5^+) = 2(5) - 5 = 5

f(5)=5f(5) = 5

The function is continuous at x=5x = 5.

Therefore, ff is continuous everywhere.


At x=0x = 0:

Left derivative: ddx(2x+5)=2\frac{d}{dx}(-2x + 5) = -2

Right derivative: ddx(5)=0\frac{d}{dx}(5) = 0

The derivatives are not equal, so ff is not differentiable at x=0x = 0.

At x=5x = 5:

Left derivative: ddx(5)=0\frac{d}{dx}(5) = 0

Right derivative: ddx(2x5)=2\frac{d}{dx}(2x - 5) = 2

The derivatives are not equal, so ff is not differentiable at x=5x = 5.


(A) ff is a continuous function everywhere → TRUE

(B) ff is a continuous function except x=5x = 5 and x=0x = 0 → FALSE

(C) ff is a continuous function except x=0x = 0 but not differentiable at x=5x = 5 → FALSE

(D) ff is a continuous function everywhere but not differentiable at x=0x = 0 and x=5x = 5 → TRUE

Statements (A) and (D) are TRUE.

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