The expression you provided, $\sqrt{-49} \times x$, contains the square root of a negative number. In mathematics, the square root of a negative number involves complex numbers.

$\sqrt{-49} = \sqrt{49} \times \sqrt{-1} = 7i$

Here, $i$ is the imaginary unit, which satisfies $i^2 = -1$. So, the expression becomes:

$\sqrt{-49} \times x = 7i \times x = 7ix$

Thus, the simplified form of the expression is $7ix$, where $i$ represents the imaginary unit.

Would you like more details on imaginary numbers or complex expressions?

Here are some related questions for further practice:

1. What is $\sqrt{-36} \times 3x$?
2. How would you simplify $(5i)^2$?
3. What is the product of $(3 + 2i) \times (1 - i)$?
4. What is the magnitude of the complex number $7i$?
5. How do you solve the quadratic equation $x^2 + 49 = 0$?

Tip: When dealing with square roots of negative numbers, remember that they always involve imaginary numbers using $i = \sqrt{-1}$.