Answer: No, you cannot.
Step-by-step explanation: A square number cannot be a perfect number.
The numbers: 0, 1, 5, 14, 30, 55, 91, 140, 204, 285, 385, 506, 650, 819, 1015, 1240, 1496, 1785, 2109, 2470, 2870, 3311, 3795, 4324, 4900, 5525, 6201 are examples of perfect numbers.
Answer:
Step-by-step explanation:
How to write numbers in standard form:
Write the first number 8.
Add a decimal point after it: 8.
Now count the number of digits after 8. There are 13 digits.
So, in standard form: 81 900 000 000 000 is 8.19 × 10¹³
Answer:
A
Step-by-step explanation:
We have the expression:

And we want to find its sign given that a>0 and b<0.
Notice that the expression is already negative since we have -4.
a>0 means that a is positive. Therefore, we can ignore it since it won’t do anything.
b<0 means that b is negative. Therefore, we will have two negatives being multiplied together. Hence, this will make a positive.
Therefore, the sign of our expression will be positive.
We can see this with an example. Let a=1 (1>0) and let b=-1 (-1<0). Then:

So, the sign is positive.
Hence, the answer is A.
Step-by-step explanation:
△BAC ≅ △EDF (given)
Therefore,
BC=EF
x-4=19
x=23