Which of the following is INCORRECT?

Correct option is D

Solution:-

$$3^\frac{1}{2}+3^\frac{1}{2}+ 3^\frac{1}{2}= 3^\frac{1}{2}× 3^\frac{1}{2}× 3^\frac{1}{2}$$​

Left Side = $$3^{1/2} + 3^{1/2} + 3^{1/2} = 3 \cdot 3^{1/2} = 3^{1/2 + 1} = 3^{3/2}$$

Right side = $$3^{1/2} \times 3^{1/2} \times 3^{1/2} = 3^{(1/2) + (1/2) + (1/2)} = 3^{3/2}$$ correct

​​$$4^\frac {1}{3}+4^\frac {1}{3}+4^\frac {1}{3}+4^\frac {1}{3}= 4^\frac {1}{3}× 4^\frac {1}{3}× 4^\frac {1}{3}× 4^\frac {1}{3}$$

Right side = $$\left(5^{1/4}\right) 5 = 5^{5/4}$$ correct

Left Side =$$6 \cdot 6 - (-6) = 6 \left( 6 + (-6) \right) = 6 \left( \frac{7}{6} \right)$$ 

​Right side = $$\left( 6 \left( \frac{6}{6} \right) \right) = 6$$  Incorrect

Thus, the correct answer is (D)