Question 10·Easy·Nonlinear Equations in One Variable; Systems in Two Variables
What is the positive solution to the equation above?
For equations where a squared expression over a number equals a constant, first clear the fraction by multiplying both sides by the denominator so you have something like . Then take the square root of both sides, remembering to include both the positive and negative roots, which gives . Solve each resulting linear equation, and finally check the question stem for any restrictions such as "positive solution" or "greater solution" to choose the correct value quickly.
Hints
Remove the fraction first
How can you get rid of the denominator 9 in so that you just have on one side?
Undo the square
Once you have an equation of the form , what operation undoes squaring? Remember that you should consider both the positive and negative results.
Solve both resulting linear equations
From , write two simple equations with equal to a positive and a negative number, then solve each for .
Answer what the question actually asks
After you find both values of , pay attention to the word "positive" in the question to decide which value to choose.
Desmos Guide
Enter the two sides of the equation as functions
In one line, type y = (x - 2)^2 / 9. In another line, type y = 16 so you have both graphs on the same coordinate plane.
Find the intersection points
Look for the points where the parabola y = (x - 2)^2 / 9 intersects the horizontal line y = 16. Click on each intersection to see its coordinates.
Choose the positive x-value
You will see two intersection points with different x-coordinates. Note both x-values, then select the one that is positive; that is the positive solution to the equation.
Step-by-step Explanation
Clear the denominator
Start with the equation:
Multiply both sides by 9 to eliminate the denominator:
Compute :
Take the square root of both sides
To undo the square on , take the square root of both sides. Remember that taking a square root gives two possible values, positive and negative:
So you get:
Write the two equations from the absolute value
The equation means that can be 12 or :
Solve both equations and choose the positive solution
Solve each equation:
For :
For :
The question asks for the positive solution, so the correct answer is .