the sum of three numbers is 81. the second number is twice the first, and the third number is six more than the second. find the
1 answer:
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Answer:
Step-by-step explanation:
<u>Errors in Algebraic Operations </u>
It's usual that students make mistakes when misunderstanding the application of algebra's basic rules. Here we have two of them
- When we change the signs of all the terms of a polynomial, the expression must be preceded by a negative sign
- When multiplying negative and positive quantities, if the number of negatives is odd, the result is negative. If the number of negatives is even, the result is positive.
- Not to confuse product of fractions with the sum of fractions. Rules are quite different
The first expression is
Let's arrange into format:
We can clearly see in all of the factors in the expression the signs were changed correctly, but the result should have been preceeded with a negative sign, because it makes 3 (odd number) negatives, resulting in a negative expression. The correct form is
Now for the second expression
Let's arrange into format
It's a clear mistake because it was asssumed a product of fractions instead of a SUM of fractions. If the result was correct, then the expression should have been
Answer:
<em>options: A,C,E </em>are correct.
Step-by-step explanation:
We have to find the expression equivalent to the expression:
we know that:
Hence,
-----(1)
A) (same as(1))
Hence, option A is correct.
B) 7 ; which is a different expression from (1)
Option B is incorrect.
C) (Same as (1))
Option C is correct.
D) which is a different expression from (1)
Hence, option D is incorrect.
E) ; which is same as (1)
Hence, Option E is correct.
F) ; which is not same as expression (1)
Hence, option F is incorrect.