Solve for X
posted by Rajesh Lal at
3:52 AM
Monday, December 22, 2008
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24 Comments:
5x^2 = 3x + 8
5x^2 - 3x - 8 = 0
(x-1)*(5x+8) = 0
so x = 1
or x = -1 3/5
No that's incorrect because when you factored the ^2 you forgot to square the 5 (or there is a misunderstanable way he puts the problem up there) so it should be like this:
25x2(squared)-3x-8
and i believ the final answer is about
x~.51 or x~-.6
Five x squared equals three x plus eight is the problem written out.
The times sign I wrote between the 5 and x and the 3 and x is required for my analysis routine, but you are correct, formally written, it would require the 2 be a superscript, but that's not possible here.
Try this
5x^2=3x+8
Is there an HTLM way of writing this?
hjg
x=-1
x=8/5
Here's your homework for today...
5x^2 = 3x * 8
5X^2 = 24x
5X^2 - 24x = 0
x(5x - 24) = 0
so x can be 0.
5x - 24 = 0
5x = 24
x = 24/5 = 4.8
So X can be 0 or 4.8, Let try them..
5(4.8)^2 = 3(4.8) * 8
5(23.04) = 14.4 * 8
115.2 = 115.2
So 4.8 works..
5(0)^2 = 3(0) * 8
5(0) = 0 * 8
0 = 0
so 0 works..
Answer. 4.8 and 0
oops.. i wrote it down wrong.. i put * 8 instead of + 8.. let me redo..
To: Euclid's Brother
That's a lot of work, but you
got the problem wrong, before the eight, there's a plus sign, not a multiply sign.
5x^2 = 3x + 8
hjg
The closest I can come up with is
x = -.3 + 12.288295i
or
x = -.3 - 12.288295i
Using the quadracic formula you end up taking the square root of -151. which is the same as sqaure root of 151 * i (imaginary number).
Unless I'm way off..
aw screw it.. it's still not right.. i missed the minus sign on the 8, so there's no imaginary number..
I came up with 92.88295 and -152.88295 using the quadratic formula, but that's not right either..
Where's my brother when I need him..
ok.. anonymouse before my first post got it right..
5x^2 = 3x + 8
5x^2 - 3x - 8 = 0
(x + 1)(5x - 8) = 0
x + 1 = 0
x = -1
5x - 8 = 0
5x = 8
x = 8/5 = 1.6
so -1 and 1.6. Plugging those back in to the original equation works.
First posted of thread got the signs backward during factoring..
subscript two is x² or alt+0178
1.0416,0.4416
the solutions are -1 and 1,6
Use the quadratic formula. X= -1 and 1.6
x= -1
x= 8/5
-1 is the obvious answer, but I couldn't find a second answer.
Solution Image
Clickety
Submitted by Harrell
5*x^2=3*x+8
5x^2=3x+8
-3x =-3x+8
2x =8
2/ =2/
x=4
I took it that ^2 is 2 to the second power. I subtracted the 3x by 5x to the 2nd power as a result of 2x. I then divided the 2x with the 8 getting x=4.
Just to let people know quadratic formula sucks
idk
WAY TOO EASY its either 23x=8 or x=8/23
Wow i can't believe i forgot the orders of operations lol so my answer of 23x=8 or x=8/23... not even close haha i can't believe i did that i'm only behind our top algebra 1 student by .4 percent doh!!!
This post has been removed by the author.
Using the quadratic equation, the answer is 1.6 and -1.
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