Question

Solve the equation. x2 18x 81 = 25 a. 14, 4 b. –4, –14 c. 14, –14 d. –4, 4

Answer 1

Answer:

The answer is the option B

$-4,-14$

Step-by-step explanation:

we know that

The formula to solve a quadratic equation of the form $ax^{2} +bx+c=0$ is equal to

$x=\frac{-b(+/-)\sqrt{b^{2}-4ac}} {2a}$

in this problem we have

$x^{2}+18x+81=25$  

$x^{2}+18x+56=0$  

so

$a=1\\b=18\\c=56$

substitute in the formula

$x=\frac{-18(+/-)\sqrt{18^{2}-4(1)(56)}} {2(1)}$

$x=\frac{-18(+/-)\sqrt{100}} {2}$

$x=\frac{-18(+/-)10} {2}$

$x1=\frac{-18+10} {2}=-4$

$x2=\frac{-18-10} {2}=-14$

Answer 2

Answer:

The correct option is B. -4 , -14  

Step-by-step explanation:

The equation is given to be : x² + 18x + 81 = 25

We need to find the roots of this given equation

⇒ x² + 18x + 81 = 25

⇒ x² + 18x + 81 - 25 = 0

⇒ x² + 18x + 56 = 0

⇒ x² + 14x + 4x + 56 = 0

⇒ x( x + 14) + 4( x + 14) = 0

⇒ (x + 14) · (x + 4) = 0

⇒ x = -14 or x = -4

Therefore, The correct option is B. -4 , -14