1.4 1.4 Rewriting Equations and Formulas Rewriting Equations and Formulas

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: Solve the following equation for y.
11x − 9y = −4
Ex: Find the value of y when x = – 4 and x = 2.
(Hint: Solve for y first.)
xy – x = 4
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 =
C + 32
More formulas that might come in handy…
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.