wtf? (1 Viewer)

[tommykins]

回复: Re: wtf?

5x^2 + 6x - 9 = 0

solve by completing the square

I did

x^2 + 6x/5 = 9/5
(x+3/5)^2=1/11/25
x= -3/5 plus or minus root 1/11/25

but dat doesn't seen to b the answer
where did i go wrong?

x^2 + 6x/5 - 9/5 = 0
x^2 + 6x/5 = 9/5
(x+3/5)^2 = 9/5 + 36/100
(x+3/5)^2 = 54/25
x+3/5 = +-(sqrt54)/5
x = (sqrt54 -3)/5 or (-sqrt54 -3)/5

 

[suzlee]

Re: 回复: Re: wtf?

x^2 + 6x/5 - 9/5 = 0
x^2 + 6x/5 = 9/5
(x+3/5)^2 = 9/5 + 36/100
(x+3/5)^2 = 54/25
x+3/5 = +-(sqrt54)/5
x = (sqrt54 -3)/5 or (-sqrt54 -3)/5

What am I doing wrong when I type the bold bit into my calculator and it gives me 2x10^-10?

 

[suneeta =)]

Re: 回复: Re: wtf?

thats what i got xD


same as tommykins


:]

 

[tommykins]

回复: Re: 回复: Re: wtf?

What am I doing wrong when I type the bold bit into my calculator and it gives me 2x10^-10?

it's (-sqrt54 - 3)/5

only difference is that it is -sqrt54 whereas the first solution is +sqrt54

 

[suzlee]

Re: 回复: Re: 回复: Re: wtf?

it's (-sqrt54 - 3)/5

only difference is that it is -sqrt54 whereas the first solution is +sqrt54

Yeah but when I check the solutions and see if they give 0 when subbed in, it keeps saying 2x10^-10

 

[tommykins]

回复: Re: 回复: Re: 回复: Re: wtf?

my calculator says it's 0.

 

[suneeta =)]

Re: 回复: Re: 回复: Re: wtf?

Yeah but when I check the solutions and see if they give 0 when subbed in, it keeps saying 2x10^-10

sub into

x^2+(6/5)x-9/5

:]

 

[Aznmichael92]

out of curiosity, how is this linked to the first question?

 

[Timothy.Siu]

out of curiosity, how is this linked to the first question?

its all maths.

 

[supercalamari]

Re: 回复: Re: wtf?

x^2 + 6x/5 - 9/5 = 0
x^2 + 6x/5 = 9/5
(x+3/5)^2 = 9/5 + 36/100
(x+3/5)^2 = 54/25
x+3/5 = +-(sqrt54)/5
x = (sqrt54 -3)/5 or (-sqrt54 -3)/5

ITT: Things that make me weep.

 

[suzlee]

Re: 回复: Re: wtf?

ITT: Things that make me weep.

lol


Okay I think my calculator is spastic

 

[aimhigh10]

this sc question just confuses me..