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Example Questions
Example Question #2 :Negative Numbers
Ifis a positive number, andis also a positive number, what is a possible value for?
Becauseis positive,必须be negative since the product of two negative numbers is positive.
Becauseis also positive,必须also be negative in order to produce a prositive product.
To check you answer, you can try plugging in any negative number for.
Example Question #1 :Negative Numbers
,, andare all negative odd integers. Which of the following three expressions must be positive?
I)
II)
III)
II only
I only
All of these
III only
None of these
All of these
A negative integer raised to an integer power is positive if and only if the absolute value of the exponent is even. Since the sum or difference of two odd integers is always an even integer, this is the case in all three expressions. The correct response is all of these.
Example Question #2 :How To Multiply Negative Numbers
is a positive integer;andare negative integers. Which of the following three expressions必须be negative?
I)
II)
III)
I and II only
I, II and III
II and III only
None of I, II or III
I and III only
None of I, II or III
A negative integer raised to an integer power is positive if and only if the absolute value of the exponent is even; it is negative if and only if the absolute value iof the exponent is odd. Therefore, all three expressions have signs that are dependent on the odd/even parity ofand, which are not given in the problem.
The correct response is none of these.
Example Question #1 :Negative Numbers
,, andare all negative numbers. Which of the following must be positive?
The key is knowing that a negative number raised to an odd power yields a negative result, and that a negative number raised to an even power yields a positive result.
:andare positive, yielding a positive dividend;is a negative divisor; this result is negative.
:andare negative, yielding a positive dividend;is a negative divisor; this result is negative.
:is positive andis negative, yielding a negative dividend;is a positive divisor; this result is negative.
:is negative andis positive, yielding a negative dividend;is a positive divisor; this result is negative.
:is positive andis negative, yielding a negative dividend;is a negative divisor; this result is positive.
The correct choice is.
Example Question #4 :How To Multiply Negative Numbers
andare positive numbers;is a negative number. All of the following必须be positive except:
Sinceandare positive, all powers ofandwill be positive; also, in each of the expressions, the powers ofandare being added. The clue to look for is the power ofand the sign before it.
In the cases ofand, since the negative numberis being raised to an even power, each expression amounts to the sum of three positive numbers, which is positive.
In the cases ofand, since the negative numberis being raised to an odd power, the middle power is negative - but since it is being subtracted, it is the same as if a positive number is being added. Therefore, each is essentially the sum of three positive numbers, which, again, is positive.
In the case of, however, since the negative numberis being raised to an odd power, the middle power is again negative. This time, it is basically the same as subtracting a positive number. As can be seen in this example, it is possible to have this be equal to a negative number:
:
Therefore,is the correct choice.
Example Question #5 :How To Multiply Negative Numbers
Letbe a negative integer andbe a nonzero integer. Which of the following必须be negative regardless of whetheris positive or negative?
None of the other answers is correct.
Sinceis positive,, the product of a negative number and a positive number, must be negative also.
Of the others:
is incorrect; ifis negative, thenis positive, andassumes the sign of.
is incorrect; again,is positive, and ifis a positive number,is positive.
is incorrect; regardless of the sign of,is positive, and if its absolute value is greater than that of,is positive.
Example Question #6 :How To Multiply Negative Numbers
Given thatare both integers,, and, which of the following is correct about the sign of the expression?
The expression must be negative.
The expression can be positive, negative, or zero.
The expression must be positive.
The expression must be positive or zero.
The expression must be negative or zero.
The expression must be negative or zero.
If, then we know thatis any number between or equal toand. Therefore必须be a negative number.
Also, if, then we know thatis any number between or equal toand. Therefore必须be a negative number.
Now looking the expressionwe can find the sign of each component in the expression.
Sinceis negative, we know that a negative number minus another number is still a negative number.
Therefore,is a negative number.
Sinceis between or equal toandwe can plug in these end values in to determine the sign of.
Therefore,is either zero or a positive number.
Now to find the sign of the expression we look at the product of the two components. The product of a negative number and a positive number is a negative number; the product of a negative number and zero is zero. Therefore, the correct choice is thatis negative or zero.
Example Question #7 :How To Multiply Negative Numbers
Find the product.
When multiplying together two negatives, our value for the product become positive.
Example Question #8 :How To Multiply Negative Numbers
Find the product.
Since we have one positive and one negative multiple, the resulting product must be negative.
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