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Pearson Algebra 2 Common Core, 2011 View details

5. Quadratic Equations

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Exercise 23 Page 229

First, rewrite the equation in standard form.

x=4 and x=- 10

Practice makes perfect

To solve the equation using our calculator with a table, we first have to rewrite the equation in standard form.

x^2+6x=40

SubEqn

LHS-40=RHS-40

x^2+6x-40=0

Having rewritten the equation in standard form, we can enter it in the calculator by pushing Y= and typing it in the first row.

Next, by pushing 2ND and GRAPH, we get a table of values for whole number inputs of x. We are looking for x-values that make the y-column equal 0.

We can already see that x=4 provides a value of 0 in the y-column. Notice that as x-values decrease the y-values also decrease. Since this is a quadratic function which opens upwards, at some point y-values must start increasing. Let's scroll up to find the second zero.

Now we can see that x=4 and x=- 10 both provide a value of 0 in the y-column. These are the zeros of the function, so the solutions to the quadratic equation are x=4 and x=- 10.

Subchapter links

Lesson Check p.229

Practice and Problem-Solving Exercises p.229-231

Standardized Test Prep p.231

Mixed Review p.231

Exercise 23 Page 229

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