a unique solution means that both lines intersect at only one distinct point. Imagine this in you head and you will release that the slope (gradient) will always have to be different.
solve both of the equations for y (so that you get smth like y=). Equate the gradients and find the value of m for which the equation holds true. Let's say when m=1, the gradients are equal. Then when m is an element of all real numbers except 1, the gradients will not be equal.
Thus our answer will be m∈R{1}. I havent actually solved the equation for myself, so idk if its 1, but I'll leave that to you.
If my explanation was not clear enough or you still have questions, shoot me a reply.
