Answer:
Yes, the number 16,641 is a perfect square.
Step-by-step explanation:
16641 is the 129th perfect square number
__________________________________________
1 2 9
1 1 66 41
1
22 66
44
249 22 41
22 41
258 0
Number = 16641
Square Root = 129
________________________________
Step-1 :
Make pair of digits of given number starting with digit at one's place. Put bar on each pair.
1 66 41
Step-2 :
Now we have to multiply a number by itself such that the product ≤ 1
Here 1×1=1≤1, So divisor is 1 and quotient is 1. Now do the division and get the remainder.
1
1 1 66 41
1
0
Step-3 :
Now , we have to bring down 66 and quotient 1 is multiplied by 2 becomes 2, which is starting digit of new divisor
1
1 1 66 41
1
2 66
Step-4 :
2 should be the digit at one's place of new divisor because when 22 is multiplied by 2 we get 44.
So new divisor is 22 and next digit of quotient is 2. Now do the division and get the remainder.
1 2
1 1 66 41
1
22 66
44
22
Step-5 :
Now , we have to bring down 41 and quotient 12 is multiplied by 2 becomes 24, which is starting digit of new divisor
1 2
1 1 66 41
1
22 66
44
24 22 41
Step-6 :
9 should be the digit at one's place of new divisor because when 249 is multiplied by 9 we get 2241.
So new divisor is 249 and next digit of quotient is 9. Now do the division and get the remainder.
1 2 9
1 1 66 41
1
22 66
44
249 22 41
22 41
0
Answer: 129 (proof 129^2) = 16,641 or 129 x 129 = 16,641
______________________________
Second Solution shortcut:
A perfect square is a number that can be expressed as the product of two equal integers.
The only way to accurately calculate if a number is a perfect square is to find the factors. Before we go through the trouble of finding the factors, there is a quick trick you can use to help determine if you need even need to do the extra work.
Try these steps first:
A number that is a perfect square never ends in 2, 3, 7 or 8. If your number ends in any of those numbers, you can stop here because your number is not a perfect square.
Obtain the digital root of the number. The digital root essentially is the sum of all of the digits. If you're lost, don't worry, we'll go over each step in more detail below.
All possible numbers that are a perfect square have a digital root of 1, 4, 7, 9.
Let's try it...
Step 1:
What is the last number of 16,641? It is this number: 16641. The answer is 1. Is 1 in the list of numbers that are never perfect squares (2, 3, 7 or 8)?
Answer: NO, 1 is not in the list of numbers that are never perfect squares. Let's continue to the next step.
Step 2:
We now need to obtain the digital root of the number. Here's how you do it:
Split the number up and add each digit together:
1 + 6 + 6 + 4 + 1 = 18
If the answer is more than one digit, you would add each digit of the answer together again:
1 + 8 = 9
What is the digital root of number 16,641?
Answer: 9
Step 3:
So now we know the digital root of 16,641 is 9. Is 9 in the list of digital roots that are always a square root (1, 4, 7 or 9)?
Answer: YES, 9 is in the list of digital roots that are always perfect squares. We can conclude that 16,641 could be a perfect square!
Factoring
OK, so now we know that 16,641 could be a perfect square. We have to find the factors of the number to be sure.
Here are all of the factors of 16,641:
1 x 16,6413 x 5,5479 x 1,84943 x 387129 x 129
Highlighted in orange above is the factor combination that makes 16,641 a perfect square. Do you see why? A number can only be a perfect square if the product of two exactly the same numbers is equal to the original number.
Here's the proof: 129 x 129 = 16,641
![60x^3+145x^2+70x=5x(12x^2+29x+14)=5x(12x^2+21x+8x+14)\\\\=5x[3x(4x+7)+2(4x+7)]=5x(4x+7)(3x+2)](https://tex.z-dn.net/?f=60x%5E3%2B145x%5E2%2B70x%3D5x%2812x%5E2%2B29x%2B14%29%3D5x%2812x%5E2%2B21x%2B8x%2B14%29%5C%5C%5C%5C%3D5x%5B3x%284x%2B7%29%2B2%284x%2B7%29%5D%3D5x%284x%2B7%29%283x%2B2%29)
