Video Transcript
Find the value of π₯ for which five π₯ plus four equals negative five.
Here weβre going to be solving a two-step equation. We can think of our goal here to isolate π₯. We want π₯ to be by itself on one side of the equal sign and everything else on the other.
In order to do that, we need to subtract four from both sides of our equation. Four minus four equals zero. Negative five minus four equals negative nine. We bring down the rest of our equation. Five π₯ plus zero equals five π₯.
I need to get rid of the five thatβs being multiplied by π₯. We multiply five by its reciprocal because one-fifth times five equals one. But if we multiply one side of the equation by one-fifth, we have to multiply the other side of the equation by one-fifth so that they remain equal.
Like weβve already said, one-fifth times five equals one. So on the left, we have one π₯ and on the right weβve multiplied negative nine by one-fifth, which equals negative nine-fifths. One π₯ equals negative nine-fifths is another way of saying π₯ equals negative nine-fifths.
