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From the first equation of the setup we learn that either y = 0 or u = c. If y = 0, then yj = 0. If u = c then from the second equation j = 0 as c < k. Taking two equations combined, we will arrive to the conclusion that yj = 0.

From the first equation of the setup we learn that either y = 0 or u = c. If y = 0, then yj = 0. If u = c then from the second equation j = 0 as c < k. Taking two equations combined, we will arrive to the conclusion that yj = 0.

How is colored portion true ?? pls explain.

In this from first equation either j=0 or u=k and from second equation either y=0 or u=c now it is given c < k so u=k & u=c cannot be true at same time. Thts why if j=0 then u=c. else if y=0 then u=k.

How do we arrive at saying: if y(u-c)=0, then u = c? it's like saying if y(x) = 0, then x = 0; I don't think so. x (expression inside the braces) can be any value, but the equation (independent variables) reduce to zero.

Am i missing something?
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KUDOS me if you feel my contribution has helped you.

If y(u - c) = 0 and j(u - k) = 0, which of the following must be true, assuming c < k?

A. yj < 0 B. yj > 0 C. yj = 0 D. j = 0 E. y = 0

y(u - c) = 0 --> u=c or y=0; j(u - k) = 0 --> u=k or j=0;

Now, the first option (u=c and u=k) cannot be simultaneously correct for both equations because if it is, then it would mean that u=c=k, but we are given that c<k. So, only one can be correct so either y=0 or j=0, which makes yj = 0 is always true.