# Page 197

Location: Chapter 21, solution to Problems 3 and 4

Note: additional solutions due to bird expressions equivalent to those given in the text.

## Problem 3 (c)

Besides the solution $$L(LL)(L(LL))$$, the following is also valid:

$L(SM)(L(SM))\;,$

## Problem 4

Besides the solution $$L(BKM)(L(BKM))$$, the following is also valid:

$L(LK)(L(LK))\;,$

## Short explanation

According to the first method illustrated in the Chapter, any bird $$A$$ is a good solution as long as it is built according to

$A = LA_1(LA_1)\;,$

where all that is needed from $$A_1$$, in turn, is that it satisfies a problem-specific condition. Hence, if more than one bird $$A_1$$ is found for a certain Problem, it automatically follows that there are more than one solution for the Problem.

For Problem 3 (c), two expressions for $$A_1$$ can be found:

$A_1yx=LLyx=SMyx=yy(xx)\;,$

and likewise for Problem 4:

$BKMyx=LKyx=yy\;.$