What are the solutions to the equation (x+5)(x-9)=21 ?

The solutions to the equation (x+5)(x-9)=21 are x=2+sqrt(70),x=2-sqrt(70)

Find the zeros of (x+5)(x-9)=21

The zeros of (x+5)(x-9)=21 are x=2+sqrt(70),x=2-sqrt(70)

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

(x + 5) (x - 9) = 21

x = 2 + 70, x = 2 - 70

Decimal Notation

x = 10.36660 \dots, x = - 6.36660 \dots

Solution steps

(x + 5) (x - 9) = 21

Expand

(x + 5) (x - 9) : x^{2} - 4 x - 45

x^{2} - 4 x - 45 = 21

Move

21

to the left side

x^{2} - 4 x - 66 = 0

Solve with the quadratic formula

x_{1, 2} = \frac{- ( - 4 ) \pm ( - 4 ) ^{2} - 4 \cdot 1 \cdot ( - 66 )}{2 \cdot 1}

(- 4)^{2} - 4 \cdot 1 \cdot (- 66) = 270

x_{1, 2} = \frac{- ( - 4 ) \pm 2 70}{2 \cdot 1}

Separate the solutions

x_{1} = \frac{- ( - 4 ) + 2 70}{2 \cdot 1}, x_{2} = \frac{- ( - 4 ) - 2 70}{2 \cdot 1}

x = \frac{- ( - 4 ) + 2 70}{2 \cdot 1} : 2 + 70

x = \frac{- ( - 4 ) - 2 70}{2 \cdot 1} : 2 - 70

The solutions to the quadratic equation are:

x = 2 + 70, x = 2 - 70

(2 x + 7)^{2} + 3 = 52

- 7 x^{2} - 8 x + 24 = 0

6 x^{2} + 3 x - 7 = 0

2 x^{2} + 9 x = 10

(2 x + 1)^{2} = 121

What are the solutions to the equation (x+5)(x-9)=21 ?
The solutions to the equation (x+5)(x-9)=21 are x=2+sqrt(70),x=2-sqrt(70)
Find the zeros of (x+5)(x-9)=21
The zeros of (x+5)(x-9)=21 are x=2+sqrt(70),x=2-sqrt(70)