Solve the quadratic equation using the method of completing the square: x2 + 7x – 21 = 0. Student solution.

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
Publisher:Carter
Chapter9: Quadratic Functions And Equations
Section9.5: Solving Quadratic Equations By Completing The Square
Problem 47PFA
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Solve the quadratic equation using the method of completing the square:
x + 7x – 21 = 0 .
Student solution.
After we move the free coefficient to the right hand side the equation becomes:
0-0
In order to have a binomial square on the left hand side, we need to add
After adding this value to the both sides, the equation becomes:
O-0-
The left hand side rewrites as the square binomial
O-0-
After we apply the square root property, we obtain
O-0 O
or
where the first value after the equal sign is positive and the second is negative.
Lastly the solutions (separate by commas) are:
= x
Transcribed Image Text:Solve the quadratic equation using the method of completing the square: x + 7x – 21 = 0 . Student solution. After we move the free coefficient to the right hand side the equation becomes: 0-0 In order to have a binomial square on the left hand side, we need to add After adding this value to the both sides, the equation becomes: O-0- The left hand side rewrites as the square binomial O-0- After we apply the square root property, we obtain O-0 O or where the first value after the equal sign is positive and the second is negative. Lastly the solutions (separate by commas) are: = x
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