Answer:
44
Step-by-step explanation:
The simplified expression of (7 + 9i)(8 - 10i) is 146 + 2i
<h3>How to simplify the expression?</h3>
The expression is given as:
(7 + 9i)(8 - 10i)
Expand the bracket
7 * 8 + 9i * 8 -7 * 10i - 9i * 10i
Evaluate the products
56 + 72i -70i - 90(i²)
Evaluate the difference
56 + 2i - 90(i²)
In complex numbers;
i² = -1
So, we have:
56 + 2i - 90(-1)
Evaluate
56 + 2i + 90
Add the like terms
146 + 2i
Hence, the simplified expression of (7 + 9i)(8 - 10i) is 146 + 2i
Read more about complex numbers at:
brainly.com/question/10662770
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Let the original 2-digit number be xy.
Because 5 times the sum of the digits is 13 less than the number, therefore
5(x + y) = 10x + y - 13
5x + 5y = 10x + y - 13
-5x + 4y = - 13 (1)
The number with reversed digits is yx.
Because 4 times the sum of the digits is 21 less than the reversed 2-digit number, therefore
4(x + y) = 10y + x - 21
4x + 4y = 10y + x - 21
3x - 6y = -21
x - 2y = -7
x = 2y - 7 (2)
Substitute (2) into (1).
-5(2y - 7) + 4y = -13
-10y + 35 + 4y = -13
-6y = -48
y = 8
From (3), obtain
x = 2*8 - 7 = 9
Answers:
The original 2-digit number is 98
The reversed 2-digit number is 89
The difference between the original and the reversed 2-digit numbers is
98 - 89 = 9
