HALL AND KNIGHT
or 'z + b + x = y + b + z'
When he was young his cousins used to say of Mr Knight:
'This boy will write an algebra  or looks as if he might.'
And sure enough, when Mr Knight had grown to be a man,
He purchased pen and paper and an inkpot, and began.
But he very soon discovered that he couldn't write at all,
And his heart was filled with yearnings for a certain Mr Hall;
Till, after many years of doubt, he sent his friend a card:
'Have tried to write an Algebra, but find it very hard.'
Now Mr Hall himself had tried to write a book for schools,
But suffered from a handicap: he didn't know the rules.
So when he heard from Mr Knight and understood his gist,
He answered him by telegram: 'Delighted to assist.'
So Mr Hall and Mr Knight they took a house together,
And they worked away at algebra in any kind of weather,
Determined not to give up until they had evolved
A problem so constructed that it never could be solved.
'How hard it is', said Mr Knight, 'to hide the fact from youth
That x and y are equal: it is such an obvious truth!'
'It is', said Mr Hall, 'but if we gave a b to each,
We'd put the problem well beyond our little victims' reach.
'Or are you anxious, Mr Knight, lest any boy should see
The utter superfluity of this repeated b?'
'I scarcely fear it', he replied, and scratched this grizzled head,
'But perhaps it would be safer if to b we added z.'
'A brilliant stroke!', said Hall, and added z to either side;
Then looked at his accomplice with a flush of happy pride.
And Knight, he winked at Hall (a very pardonable lapse).
And they printed off the Algebra and sold it to the chaps.

or 'z + b + x = y + b + z'
When he was young his cousins used to say of Mr Knight:
'This boy will write an algebra  or looks as if he might.'
And sure enough, when Mr Knight had grown to be a man,
He purchased pen and paper and an inkpot, and began.
But he very soon discovered that he couldn't write at all,
And his heart was filled with yearnings for a certain Mr Hall;
Till, after many years of doubt, he sent his friend a card:
'Have tried to write an Algebra, but find it very hard.'
Now Mr Hall himself had tried to write a book for schools,
But suffered from a handicap: he didn't know the rules.
So when he heard from Mr Knight and understood his gist,
He answered him by telegram: 'Delighted to assist.'
So Mr Hall and Mr Knight they took a house together,
And they worked away at algebra in any kind of weather,
Determined not to give up until they had evolved
A problem so constructed that it never could be solved.
'How hard it is', said Mr Knight, 'to hide the fact from youth
That x and y are equal: it is such an obvious truth!'
'It is', said Mr Hall, 'but if we gave a b to each,
We'd put the problem well beyond our little victims' reach.
'Or are you anxious, Mr Knight, lest any boy should see
The utter superfluity of this repeated b?'
'I scarcely fear it', he replied, and scratched this grizzled head,
'But perhaps it would be safer if to b we added z.'
'A brilliant stroke!', said Hall, and added z to either side;
Then looked at his accomplice with a flush of happy pride.
And Knight, he winked at Hall (a very pardonable lapse).
And they printed off the Algebra and sold it to the chaps.
