Question 2 of 5

Select the correct answer.

Two quadratic equations are shown below.

Equation A: [tex]x^2 + bx - 8 = 47[/tex]

Equation B: [tex](x + 3)^2 = 64[/tex]

Determine what value of [tex]b[/tex] causes Equation A and Equation B to have the same solutions.

A. 6
B. -3
C. -8
D. 3



Answer :

To determine what value of [tex]\( b \)[/tex] causes Equation A and Equation B to have the same solutions, follow these steps:

1. Solve Equation B:
[tex]\((x + 3)^2 = 64\)[/tex]

To find the solutions for [tex]\( x \)[/tex], we take the square root of both sides first:

[tex]\[ x + 3 = \pm \sqrt{64} \][/tex]

[tex]\[ x + 3 = \pm 8 \][/tex]

This results in two separate equations:

[tex]\[ x + 3 = 8 \quad \text{or} \quad x + 3 = -8 \][/tex]

2. Solve for [tex]\( x \)[/tex]:

For [tex]\( x + 3 = 8 \)[/tex]:

[tex]\[ x = 8 - 3 = 5 \][/tex]

For [tex]\( x + 3 = -8 \)[/tex]:

[tex]\[ x = -8 - 3 = -11 \][/tex]

So, the solutions for Equation B are [tex]\( x = 5 \)[/tex] and [tex]\( x = -11 \)[/tex].

3. Substitute [tex]\( x \)[/tex] values from Equation B into Equation A:

Equation A: [tex]\( x^2 + bx - 8 = 47 \)[/tex]

For [tex]\( x = 5 \)[/tex]:

[tex]\[ 5^2 + b(5) - 8 = 47 \][/tex]

Simplify:

[tex]\[ 25 + 5b - 8 = 47 \][/tex]

[tex]\[ 17 + 5b = 47 \][/tex]

Subtract 17 from both sides:

[tex]\[ 5b = 30 \][/tex]

Divide by 5:

[tex]\[ b = 6 \][/tex]

For [tex]\( x = -11 \)[/tex]:

[tex]\[ (-11)^2 + b(-11) - 8 = 47 \][/tex]

Simplify:

[tex]\[ 121 - 11b - 8 = 47 \][/tex]

[tex]\[ 113 - 11b = 47 \][/tex]

Subtract 113 from both sides:

[tex]\[ -11b = -66 \][/tex]

Divide by -11:

[tex]\[ b = 6 \][/tex]

Therefore, the value of [tex]\( b \)[/tex] that causes Equation A and Equation B to have the same solutions is [tex]\( \boxed{6} \)[/tex].