FORM 4 MATH

wing han

2009-09-04 3:46 am

find the values of x and y where x and y are real numbers.

(x+y)+(x-y)i=12+6i 點計><幫幫手呀

更新1:

仲有幾題>< 2.If x and y are real numbers and (x+3yi)+(y-4xi)=8-11i, find the values of x and y. 3.suppose x and y are real numbers and (x+3yi)+2(y-5i)-(7-2xi)=0 ,find the values of x and y . 4.simolift (10+9i)(-1-11i)+3(5-4i). 真系5該曬呀><我做到呢3題5識做>

回答 (1)

用戶9112

2009-09-04 3:59 am

✔ 最佳答案

(x + y) + (x - y)i =12 + 6i
Compare Real parts and Imaginary parts
x + y = 12... (1)
x - y = 6 ...(2)
(1) + (2) => 2x = 18
x = 9
Sub into (1)
9 + y = 12
y = 3

2009-09-03 23:05:37 補充：
(x + 3yi) + (y - 4xi) = 8 - 11i
(x + y) + (3y - 4x)i = 8 - 11i
x + y = 8 => 4x + 4y = 32 ... (1)
3y - 4x = -11 ...(2)
(1) + (2) => 7y = 21 and y = 3 => x = 5

2009-09-03 23:06:17 補充：
(x + 3yi) + 2(y - 5i) - (7 - 2xi) = 0
(x + 2y - 7) + (3y - 10 + 2x)i = 0
x + 2y - 7 = 0 or 2x + 4y - 14 = 0 ...(1)
3y - 10 + 2x = 0 ...(2)
(1) - (2) => y - 4 = 0 or y = 4 => x = -1

2009-09-03 23:07:07 補充：
(10 + 9i)(-1 - 11i) + 3(5 - 4i)
= -10 - 110i - 9i + 99 + 15 - 12i
= 104 - 131i

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