Tìm x, y thuộc Z; biết: x - 4/ y -3 = 4/ 3 và x - y = 5
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Question

Tìm x, y thuộc Z; biết: x - 4/ y -3 = 4/ 3 và x - y = 5

huong1901 · Answer

Ta có :
x - 4/ y -3 = 4/ 3 ( điều kiện : y khác 3 )
⇔ 3( x-4) = 4(y-3)
⇔ 3x-12=4y-12
⇔ 3x = 4y  (1)
Vì x - y = 5 ⇒ x =5+y (2)
Thay (2) vào (1) , ta được :
3(5+y) = 4y
⇔ 15 + 3y =4y
⇔ y = 15 ( thỏa mãn đk ) 
thay y=15 vào (2) , được : x= 5+15 = 20
Vậy x=20 và y=15
~ Chúc bạn học tốt ~

huyminh470 · Answer

Ta có: x&#x2212;4y&#x2212;3=43" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">x−4/y−3 = 4/3  
&#x21D2;(x&#x2212;4)3=(y&#x2212;3)4" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒(x−4)3=(y−3)4⇒(x−4)3=(y−3)4
&#x21D2;3x&#x2212;12=4y&#x2212;12" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒3x−12=4y−12⇒3x−12=4y−12
&#x21D2;3x&#x2212;4y=0" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒3x−4y=0⇒3x−4y=0
&#x21D2;3x=4y" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒3x=4y⇒3x=4y
&#x21D2;x4=y3" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒x4=y3⇒x4=y3
Áp dụng t/c dãy tỉ số bằng nhau ta có:
x/4 = y/3 = x−y/4−3 = 5
Do [x4=5y3=5" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">[x/4 = 5 và [x4=5y3=5" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">y/3 = 5
[x4=5y3=5" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">⇒[x=20 và  y=15
[x4=5y3=5" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">Vậy suy ra [x=20y=15" role="presentation" style="box-sizing: border-box; display: inline; font-weight: normal; line-height: normal; font-size: 16px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;" tabindex="0">[x=20 và  y=15

Tìm x, y thuộc Z; biết: x - 4/ y -3 = 4/ 3 và x - y = 5

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Tìm x, y thuộc Z; biết: x - 4/ y -3 = 4/ 3 và x - y = 5

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