SOLUTION: I really need help with this question, I'm not understanding it at all, the answer apparently is (-3/2i , 15/4i), (3/2i, -15/4i) Solve this System: 9x^2-4

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: I really need help with this question, I'm not understanding it at all, the answer apparently is (-3/2i , 15/4i), (3/2i, -15/4i) Solve this System: 9x^2-4      Log On


   



Question 290479: I really need help with this question, I'm not understanding it at all, the answer apparently is (-3/2i , 15/4i), (3/2i, -15/4i) Solve this System: 9x^2-4y^2=36
5x+2y=0

Found 3 solutions by richwmiller, subudear, ankor@dixie-net.com:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
Everyone here needs help. You don't need to remind us.
No one understands the problems or they wouldn't be here. Don't remind us.
Correct English: I do not understand it at all.
Incorrect English: I am not understanding it at all. We cannot say "am not understanding". Some verbs just do not use that form at all.

Answer by subudear(62) About Me  (Show Source):
You can put this solution on YOUR website!
Given
9x^2-4y^2=36
it can be written as
(3x)^2-(2y)^2=36
or
(3x-2y)(3x+2y)=36 because a^2-b^2=(a-b)(a+b)
now also it is given that 5x + 2y = 0 or 2y = -5x
replace this vlaue in the above equation we get
(3x + 5x)(3x - 5x)=36
-16x^2 =36
x = (3/2)i, -(3/2)i
putting values of x in 2y = -5x we get
(-3/2i , 15/4i), (3/2i, -15/4i)

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Solve this System:
9x^2 - 4y^2 = 36
5x + 2y = 0
:
2y = -5x
y = -5%2F2x
or
y = -2.5x
:
Replace y with -2.5x in the 1st equation
9x^2 - 4(-2.5x)^2 = 36
9x^2 - 4(6.25x^2) = 36
9x^2 - 25x^2 = 36
-16x^2 = 36
16x^2 = -36
4x = +/-sqrt%28-36%29
4x = +6i
x = 6%2F4i
x = 3%2F2i
and
4x = -6i
x = -6%2F4i
x = -3%2F2i
:
Find y using the 2nd equation when x =3%2F2i
5(3%2F2i) + 2y = 0
15%2F2i + 2y = 0
2y = -15%2F2i
y = -15%2F4i
and find y when x = -3%2F2i
5(-3%2F2i) + 2y = 0
-15%2F2i + 2y = 0
2y = +15%2F2i
y = +15%2F4i