0.2x^2+1.2=3.4
-3.31662
but i only have 4 blocks of answers i could put there.
am i wrong.
(x+3)(x-3)=16-2x^2
my answers is
5
---
√3
how am i wrong
2007-09-23 10:10:38 · 6 answers · asked by hola_kity2008 1 in Science & Mathematics ➔ Mathematics
the first answer is 3.31, not -3.31.
second answer:
x^2-9=16-2x^2
3x^2=25
x=(25/3)^0.5
x=2.89
2007-09-23 10:19:32 · answer #1 · answered by samuelll 2 · 0⤊ 0⤋
First of all, you are wrong (but you got very close!) because you have X raised to the power of two. THAT means, for each formula, you *can* have up to two answers.
The first one:
0.2x^2+1.2=3.4
0.2x^2 = 3.4 - 1.2
0.2x^2 = 2.2
x^2 = 11
x = +/- sqrt(11) You forgot the plus or minus part
The second one:
(x+3)(x-3)=16-2x^2
x^2 - 9 = 16 - 2x^2
x^2 + 2x^2 = 16 + 9
3x^2 = 25
x = sqrt(25)/sqrt(3)
x= +/- 5/sqrt(3)
Once again, you forgot plus or minus.
When you square something, reagardless of the original number was plus or minus, you always end up with positive. Therefore, going backwards, you have to consider both possibilities.
2007-09-23 10:19:49 · answer #2 · answered by tkquestion 7 · 0⤊ 0⤋
I have to guess, but it looks like you got x - sqrt(11) = plus or minus 3.31662... Why did you pick the negative value?
For the second problem, the answers are plus or minus 5 / sqrt(3).
2007-09-23 10:22:01 · answer #3 · answered by morningfoxnorth 6 · 0⤊ 0⤋
0.2x^2+1.2=3.4 (sr = square root of)
(n = natural)
0.2x^2=2.2
1/10x^2=11/5
1/10x=sr-11/5 rationalize denom. sr-11*5/n-5
sr-55/n-5
x= 10 * sr-55/n-5
x= 2sr-55
2007-09-23 10:20:06 · answer #4 · answered by Ryan 1 · 0⤊ 0⤋
multiply the top equation by 10, simplify, and take the square root of both sides.
Expand the second equation, collect like terms, and take the square root of both sides.
Don't forget you'll get a + and - answer
2007-09-23 10:20:34 · answer #5 · answered by Bonhomme 1 · 0⤊ 0⤋
i am not sure, your answer to me looks right
2007-09-23 10:15:53 · answer #6 · answered by ..... 3 · 0⤊ 0⤋