Help please with a question (1 Viewer)

[DARA92]

Q: Which 2-digit number is equal to the sum of its first digit plus the square of its second digit?

please show how you work out, thanks.

 

[SunnyScience]

89.


(I googled it...sorry, I don't have the working out.)

 

[Sy123]

Q: Which 2-digit number is equal to the sum of its first digit plus the square of its second digit?

please show how you work out, thanks.

Let x and y be integers from 0 to 9 (inclusive)
And x is the first digit and y is the second
Let z be the number we are looking for, according to your property











Now if put x in and it comes out that y is an integer, then that pair of x and y are the ones we are looking for, we will only take the + case becasue we are only looking at positive numbers here

So put in your calculator







.
.
.



The one that gives us an integer is 8.

So x=8

y=9

Therefore the number is 89

(obviously there are more elegant ways to find what numbers of 1+36x are square)

 

[anomalousdecay]

You know that question once came up in a 4-unit paper.