Some questions on the SAT are one-step equations. For instance consider the following equation:
What value of x is the solution to the given equation?
We can solve this by isolating x, we can do that by subtracting 40 from both sides of the equation:
You can also solve this using Desmos. Consider the image below:
In the following problem, you have fractions to deal with:
Xello highlights us multiplying across by the least common multiple of all three numbers, 36, but we could also just put this in Desmos:
From this image we can go to where the line crosses the x-axis and see that our solution is x = 2.
Consider the following problem from Xello:
If 6x = 48, what is the value of 5x?
You could solve this by solving for x and then multiplying by 5, or just put both 6x = 48 and 5x into Desmos and take the y-value of where the lines interect:
Our solution is 40.
Here is one that is more difficult:
We could figure this out but let's just use Desmos, we just need to switch t to x:
We can see here that 2x ... eh hem, 2t = 50, so 50 is our solution.
Let's try another one:
If 7x + 21 = -2, what is x + 3?
We can use Desmos, but we'll have to zoom in:
And then figure out the value that works: -2/7
In class, we'll continue with this section ...