Help with Quadratic Equations by completing the square

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SUMMARY

The discussion focuses on solving quadratic equations by completing the square, specifically when the quadratic term is isolated on one side of the equation. The example provided is x² = 14x - 33, which can be rearranged to x² - 14x + 33 = 0. Participants clarify the process of completing the square by taking the coefficient of the linear term (-14), dividing it by 2 to get -7, squaring it to obtain 49, and then adding 49 to both sides of the equation. This method leads to the equation x² - 14x + 49 = 16, which can then be solved for x.

PREREQUISITES
  • Understanding of quadratic equations
  • Familiarity with the method of completing the square
  • Basic algebraic manipulation skills
  • Knowledge of solving equations
NEXT STEPS
  • Practice completing the square with various quadratic equations
  • Explore the quadratic formula for solving equations
  • Learn about the discriminant and its role in determining the nature of roots
  • Study graphing quadratic functions to visualize solutions
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Students learning algebra, educators teaching quadratic equations, and anyone seeking to improve their problem-solving skills in mathematics.

Maddsnicole
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I understand how to solve these equations when the square is on this side of the equal sign: x2 + 8x + 7 = 27

But when the square is on the other side, I am thrown. Like this one...
x2 = 14x - 33

The solutions manual shows the next step as the following, but what do you do to get to this point?
x2 - 14x + 49 = -33 + 49
 
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We are given:

$$x^2=14x-33$$

Subtract through by $14x$:

$$x^2-14x=-33$$

Take the coefficient of the linear term which is -14, divide by 2 to get -7, then square to get 49, and so add 49 to both sides:

$$x^2-14x+49=-33+49$$

Does this make sense?
 
Maddsnicole said:
I understand how to solve these equations when the square is on this side of the equal sign: x2 + 8x + 7 = 27

But when the square is on the other side, I am thrown. Like this one...
x2 = 14x - 33

The solutions manual shows the next step as the following, but what do you do to get to this point?
x2 - 14x + 49 = -33 + 49

I would not have followed the solution manuals next step. From the question

x2 = 14x - 33

I would first move everything over to the left hand side (because this is where the x2 is).

When you do this the terms you move from one side to the other need to change signs (positive becomes negative, negative becomes positive) so you should get this:

x2 - 14x + 33 = 0

From here I would complete the square as normal.
 

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