Tuesday, March 19, 2013

Quadratic Equations with Square Roots

Introduction :

In mathematics, a quadratic equation is one of a polynomial equation of the second degree. The general form is

ax^2+bx+c=0

Where x represent a variable, and a, b, and c, are the constants, with a ? 0. (If a = 0, the equation becomes a linear equation.). The constants a, b, and c, are called, the quadratic coefficient, the linear coefficient and the constant term or free term. The word "quadratic" comes from quadratus; it is the Latin word for "square." Quadratic equations can also be solved by factoring, completing the square, graphing, Newton's method, and using the quadratic formula.

Source: wikipedia


Example problems on Quadratic equations with square roots:

Example 1:

Determine all real solutions to the equation

Sqrt (x + 1) = 4

Solution:

Given equation is
sqrt (x + 1) = 4

Squaring on both sides, then the above equation becomes
[sqrt (x + 1)]^2 = 4^2

Simplify the above equation
x + 1 = 16

Solve for x.
x = 15

NOTE: Because we squared both sides not including putting any conditions, extraneous solutions may be introduced, checking the solutions is necessary.

Check the left side (LS) of the given equation when x = 15

LS = sqrt (x + 1) = sqrt (15 + 1) = 4

Check the right Side (RS) of the given equation when x = 15

RS = 4

When x = 15, the left and the right sides of the given equation are equal: x = 15 is a solution to the given equation.

Example 2:

Determine all real solutions of the equation

Sqrt (3 x + 1) = x - 3

Solution:

Given equation is
sqrt ( 3 x + 1) = x - 3

Squaring on both sides, then the above equation becomes
[sqrt ( 3 x + 1) ]^2 = (x - 3)^2

Simplify the above equation
3 x + 1 = x^2 - 6 x + 9

Rewrite the above equation in factor form.
x^2 - 9 x + 8 = 0

The above form is a quadratic equation with 2 solutions
x = 8 and x = 1


Practice problems on quadratic equations with square roots:


1) Determine the real value of the given quadratic equation with square roots.

Sqrt (2 x + 15) = 5
Answer: x = 5

2) Determine the real value of the given quadratic equation with square roots.

Sqrt (4 x - 3) = x – 2

Answer: x = 7

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