Root Formula: Solve x² + 7¾x - 2 Using Step-by-Step Method

Question

Use the root formula and extract the trinomial

x2+734x2 x^2+7\frac{3}{4}x-2

Video Solution

Solution Steps

00:00 Factorize the trinomial using the roots formula
00:03 Let's identify the coefficients
00:13 We'll use the roots formula to find possible solutions
00:24 We'll substitute appropriate values and solve to find solutions
00:35 Let's calculate the root
00:48 We'll find the 2 possible solutions (addition and subtraction)
00:51 These are the solutions, we'll use them to construct the trinomial
00:59 Let's find what zeros each solution
01:04 These will be the products of the trinomial
01:10 And this is the solution to the problem

Step-by-Step Solution

The quadratic equation given is:

x2+734x2=0 x^2 + 7\frac{3}{4}x - 2 = 0

First, let's rewrite the coefficient b b as a decimal for simplicity:

b=734=7.75 b = 7\frac{3}{4} = 7.75

Given a=1 a = 1 , b=7.75 b = 7.75 , and c=2 c = -2 , we apply the quadratic formula:

x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Calculate the discriminant:

Discriminant=b24ac=(7.75)24×1×2 \text{Discriminant} = b^2 - 4ac = (7.75)^2 - 4 \times 1 \times -2

=60.0625+8=68.0625 = 60.0625 + 8 = 68.0625

Now, find the roots by plugging into the quadratic formula:

x=7.75±68.06252 x = \frac{-7.75 \pm \sqrt{68.0625}}{2}

Calculate the square root:

68.0625=8.25 \sqrt{68.0625} = 8.25

Find the roots:

x1=7.75+8.252=0.52=0.25 x_1 = \frac{-7.75 + 8.25}{2} = \frac{0.5}{2} = 0.25

x2=7.758.252=162=8 x_2 = \frac{-7.75 - 8.25}{2} = \frac{-16}{2} = -8

Thus, the factored form of the trinomial can be written using these roots:

(xx1)(xx2)=(x0.25)(x+8) (x - x_1)(x - x_2) = (x - 0.25)(x + 8)

Rewriting with fractional representations:

(x14)(x+8) (x - \frac{1}{4})(x + 8)

Thus, the trinomial can be expressed as:

(x+8)(x14) (x + 8)(x - \frac{1}{4})

Comparing with the options provided, the correct answer is:

(x+8)(x14) \boxed{(x + 8)(x - \frac{1}{4})}

Answer

(x+8)(x14) (x+8)(x-\frac{1}{4})