Descartes' rule of signs
Descartes' Rule of Signs is about counting how many positive and negative answers you will get when solving an equation with only numbers and variables. It comes from the French philosopher Rene Descartes in the 17th century.
Here is an example of how to use Descartes' Rule of Signs. Let's say you have an equation like this one: 3x² - 5x + 2 = 0. You would look at the equation, and count the number of positive numbers (or "plus signs") and negatives numbers (or "minus signs"), not including any numbers next to the variables (the "x"). In this equation, there are two positives (the 3 and the 2) and one negative (the -5).
According to Descartes' Rule of Signs, having two positives and one negative means that there are either zero, one, or two possible answers to the equation. So there could be no solutions, one solution, or two solutions to this equation.
Descartes' Rule of Signs is a useful tool when solving equations because it can help you quickly find out the number of solutions to the equation.
Here is an example of how to use Descartes' Rule of Signs. Let's say you have an equation like this one: 3x² - 5x + 2 = 0. You would look at the equation, and count the number of positive numbers (or "plus signs") and negatives numbers (or "minus signs"), not including any numbers next to the variables (the "x"). In this equation, there are two positives (the 3 and the 2) and one negative (the -5).
According to Descartes' Rule of Signs, having two positives and one negative means that there are either zero, one, or two possible answers to the equation. So there could be no solutions, one solution, or two solutions to this equation.
Descartes' Rule of Signs is a useful tool when solving equations because it can help you quickly find out the number of solutions to the equation.
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