1.4 Rewriting Equations and Formulas
Many equations involve more than one variable. It is often necessary to rewrite an
equation or formula by isolating a single variable.
Ex:
Ex: Solve the following equation for y.
11x − 9y = −4
Ex:
Ex: Find the value of y when x = – 4 and x = 2.
(Hint: Solve for y first.)
xy – x = 4
Ex:
Ex: Solve each formula for the underlined variable.
a.) P = 2l + 2w
(Perimeter of a rectangle)
b.) A = π r 2
(Area of a circle)
c.) F =
9
C + 32
5
More formulas that might come in handy…
(Temperature)
Try the following…
Find the radius of a circle with a circumference of 25 feet.
Solve the formula P = 2l + 2w for l. Then find the length of a rectangle with a
width of 7 inches and a perimeter of 30 inches.
Solve the formula A = lw for w. Then find the width of a rectangle with a
length of 16 meters and an area of 40 square meters.