Write the quadratic equation and solve by using the general formula. "Find two consecutive numbers in which the double of the square of the smaller number plus the square of the greater number is 121"

Respuesta :

Answer: 6 and 7

Step-by-step explanation:

Let the numbers be x and x + 1

We can form and equation as:

2(x²) + (x+1)² = 121

2x² + (x + 1)(x + 1) = 121

2x² + x² + x + x + 1 = 121

3x² + 2x = 121 - 1

3x² + 2x = 120

3x² + 2x - 120 = 0

3x² - 18x + 20x - 120 = 0

3x(x - 6) + 20(x - 6)

Therefore, x - 6 = 0

x = 0 + 6

x = 6

The numbers are 6 and 7

The two numbers given in the statement is required.

The two numbers can be [tex]6,7[/tex] or [tex]-\dfrac{20}{3},-\dfrac{17}{3}[/tex]

Quadratic equation

Let [tex]x[/tex] be the first number

[tex]x+1[/tex] be the next consecutive number

From the statement we get

[tex]2x^2+(x+1)^2=121\\\Rightarrow 2x^2+x^2+2x+1=121\\\Rightarrow 3x^2+2x-120=0\\\Rightarrow x=\dfrac{-2\pm \sqrt{2^2-4\times3\left(-120\right)}}{2\times3}\\\Rightarrow x=6,-\dfrac{20}{3}[/tex]

If [tex]x=6[/tex]

the other number is [tex]x+1=6+1=7[/tex]

If [tex]x=-\dfrac{20}{3}[/tex]

the other number is [tex]x+1=-\dfrac{20}{3}+1=-\dfrac{17}{3}[/tex]

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