Question

Solve the equation. x2 18x 81 = 25

a. 14, 4
b. –4, –14
c. 14, –14
d. –4, 4

Answer 1

The correct option is B. -4 , -14

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

Answer 2

The answer is the option B

`-4,-14`

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(+/-)√(100)} {2}`

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

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

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