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3 years ago

If now Lina is three times as old as Nick, and in 6 years she will be twice as old as he, how old are they now?\

Mathematics

1 answer:

Kitty [74]3 years ago

8 0

Answer:

Step-by-step explanation:

Nick's age = x years

Lina's age =3*x = 3x

After 6 years,

Lina's age = 3x + 6

Nick's age = x + 6

3x + 6 = 2*(x+6)

3x + 6 = 2*x + 2*6

3x + 6 = 2x + 12 {Subtract 6 form both sides}

3x +6 - 6 = 2x + 12 - 6

3x = 2x + 6 {subtract 2x from both sides}

3x - 2x = 2x + 6 - 2x

x = 6

Nick's age = 6 years

Lina's age =3*6 = 18 years

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andrey2020 [161]

First observe that if $a+b>0$ ,

$(a + b)^2 = a^2 + 2ab + b^2 \\\\ \implies a + b = \sqrt{a^2 + 2ab + b^2} = \sqrt{a^2 + ab + b(a + b)} \\\\ \implies a + b = \sqrt{a^2 + ab + b \sqrt{a^2 + ab + b(a+b)}} \\\\ \implies a + b = \sqrt{a^2 + ab + b \sqrt{a^2 + ab + b \sqrt{a^2 + ab + b(a+b)}}} \\\\ \implies a + b = \sqrt{a^2 + ab + b \sqrt{a^2 + ab + b \sqrt{a^2 + ab + b \sqrt{\cdots}}}}$

Let $a=0$ and $b=x$ . It follows that

$a+b = x = \sqrt{x \sqrt{x \sqrt{x \sqrt{\cdots}}}}$

Now let $b=1$ , so $a^2+a=4x$ . Solving for $a$ ,

$a^2 + a - 4x = 0 \implies a = \dfrac{-1 + \sqrt{1+16x}}2$

which means

$a+b = \dfrac{1 + \sqrt{1+16x}}2 = \sqrt{4x + \sqrt{4x + \sqrt{4x + \sqrt{\cdots}}}}$

Now solve for $x$ .

$x = \dfrac{1 + \sqrt{1 + 16x}}2 \\\\ 2x = 1 + \sqrt{1 + 16x} \\\\ 2x - 1 = \sqrt{1 + 16x} \\\\ (2x-1)^2 = \left(\sqrt{1 + 16x}\right)^2$

(note that we assume $2x-1\ge0$ )

$4x^2 - 4x + 1 = 1 + 16x \\\\ 4x^2 - 20x = 0 \\\\ 4x (x - 5) = 0 \\\\ 4x = 0 \text{ or } x - 5 = 0 \\\\ \implies x = 0 \text{ or } \boxed{x = 5}$

(we omit $x=0$ since $2\cdot0-1=-1\ge0$ is not true)

3 0

1 year ago

Given one zero of the polynomial function, find the other zeros.

OLga [1]

Answer:

8. $-\frac{1}{9}$ and 1

9. $-\frac{1}{2}$ and -5

Step-by-step explanation:

Hope this helps ;)

7 0

2 years ago

Does anybody know the answer?

soldi70 [24.7K]

Answer:

tha answer to the question is B. 2

7 0

2 years ago

Which function in vertex form is equivalent to f(x) = x^2 + 6x + 3?

OlgaM077 [116]

$f(x)=x^2+6x+3$

Complete the square:

$x^2+6x+a^2\implies a=\dfrac{6x}{2x}=3\implies x^2+6x+3^3$

And we have:

$f(x)=x^2+6x+3\\\\f(x)=x^2+6x+3^2-3^2+3\\\\f(x)=(x+3)^2-9+3\\\\\boxed{f(x)=(x+3)^2-6}$

Answer B.

3 0

3 years ago

What is the slope and y-intercept of (0,8) (1,10) (2,12) (3,14) (4,16) (5,18)

Anna71 [15]

To get slope use

y2 - y1 / x2 - x1

10 - 8 / 1 - 0 = 2/1 = 2

Slope = 2

The y-intercept is the coordinate point that has 0 as the x value.

(0, 8) is the y-intercept.

4 0

2 years ago