Page 687 - Algebra 1

Example
2
Solving Quadratic Equations Using a Graphing Calculator
Solve each equation by graphing the related function on a graphing calculator.
a. -6x-9=x2
SOLUTION
Write the equation in standard form.
-x2 -6x-9=0
Graph the related function
f(x)=-x2 -6x-9.
The graph appears to have an x-intercept at -3.
Use the Table function to determine the zeros of this function. The solution is -3.
b. -6x=-x2 -13
SOLUTION
Write the equation in standard form.
x2 -6x+13=0.
Graph the related function f (x) = x2 - 6x + 13.
The graph opens upward and does not intersect the x-axis.
There is no solution.
c. -3x2 +5x=-7
Round to the nearest tenth.
SOLUTION
Write the equation in standard form.
-3x2 +5x+7=0
Graph the related function f(x)=-3x2 +5x+7.
The graph appears to have x-intercepts at 3 and -1.
Use the Zero function to determine the zeros of this function. Round to the nearest tenth.
The solutions are x = 2.6 and -0.9.
Hint
For help with graphing quadratic functions, see Graphing Calculator Lab 8: Characteristics of Parabolas on p. 583.
672 Saxon Algebra 1