Easy or not?

Algebra Level 1

Find the values of x x and y y with x 0 x \neq 0 .

x = y = 3 x=y=\sqrt{3} x = y = 2 x=y=2 or x = y = 2 x=y=-2 x = y = 1 x=y=1 or x = y = 1 x=y=-1 x = y = 2 x=y=\sqrt{2}

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

3 solutions

Here is my solution. Let's mark each equation as (1) and (2). Since x 0 x\neq0 so:

( 1 ) 2 ( y x ) 2 1 = 1 x 2 (1)\Leftrightarrow 2(\frac{y}{x})^2-1=\frac{1}{x^2} and ( 2 ) 2 ( y x ) 3 = 2. y x . 1 x 2 1 x 2 (2)\Leftrightarrow 2-(\frac{y}{x})^3=2.\frac{y}{x}.\frac{1}{x^2}-\frac{1}{x^2} .

Subtitute like this:

a = y x a=\frac{y}{x} and b = 1 x 2 b=\frac{1}{x^2} .

Do that and we have a new system:

2 a 2 1 = b 2a^2-1=b ( 3 ) (3) and 2 a 3 = 2 a b b 2-a^3=2ab-b ( 4 ) (4)

From ( 3 ) (3) and ( 4 ) (4) a = 1 \Rightarrow a=1 which means:

y x = 1 y = x \frac{y}{x}=1\Leftrightarrow y=x .

Combine it with ( 1 ) (1) and we have the following result:

x = y = 1 x=y=1 or x = y = 1 x=y=-1 .

Solution ends.

Kelly Bumr
Sep 23, 2014

let y=kx and substitute into the to equations. divide the second by the first equation. There we go

More exactly it must be y=ax+b. Not many people can have quick judgement.

Nguyễn Hữu Khánh - 6 years, 8 months ago

Log in to reply

yeah sure. just made it quicker :p

Kelly Bumr - 6 years, 8 months ago
Muhammad Khokhar
Sep 21, 2014

that's pretty easy!! as you can place each of the options in given equation! :P

Of course it is. If you solve it properly, you will see why I put x 0 x\neq0 there.

Nguyễn Hữu Khánh - 6 years, 8 months ago

Log in to reply

4 đáp án có x=y thì dễ ròi ;)

Kelly Bumr - 6 years, 8 months ago

Log in to reply

Nếu không có 4 lựa chọn?

Nguyễn Hữu Khánh - 6 years, 8 months ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...