A Guide to the GRE/Positives and Negatives

Positives & Negatives Subtracting a negative is the same as adding a positive. 5 - -3 = 5 + 3 = 8 Adding a negative is the same as subtracting a positive. 2 + -5 = 2 – 5 = -3 Multiplying a negative and a positive equals a negative. 5(-3) = -15 Multiplying a negative and a negative equals a positive. -7(-3) = 7(3) = 21 Thus, multiplying any odd number of negatives together equals a negative, while multiplying any even number of negatives together equals a positive. Practice 1. What is the value of 8(-4)? 2. If -2 - y is positive, then is y negative or positive? 3. x^77 is positive. Is x negative or positive? Answers to Practice Questions 1. -32 Multiplying a positive by a negative equals a negative. 2. y must be negative (and must be less than -2) Subtracting a negative is the same as adding a positive. For example, y could equal -3. -2 - -3 = -2 + 3 = 1. 3. x must be positive. A negative multiplied by a negative equals a positive (e.g., -1 ✕ -1 = 1), while a positive multiplied by a negative equals a negative (e.g., (-1 ✕ -1) ✕ -1 = 1 ✕ -1 = -1). Therefore, -1(-1)(-1) is negative, while -1(-1)(-1)(-1) is positive. Thus, any time an odd number of negatives are multiplied together, they equal a negative - meaning x must be positive, since 77 xs multiplied together are positive.