Đáp án: Câu 2

= $\begin{cases} 2 ( x + 1 ) - 15 ( y - 1 ) = 8\\3 ( x + 1 ) - 2 ( y - 1 ) = 1\\ \end{cases}$

<=> $\begin{cases} 6 ( x + 1 ) - 45 ( y - 1 ) = 24\\6 ( x + 1 ) - 4 ( y - 1 ) = 2\\ \end{cases}$

<=> $\begin{cases} -41 ( y - 1 ) = 22\\6 ( x + 1 ) - 4 ( y - 1 ) = 2\\ \end{cases}$ <=> $\begin{cases} y - 1 = \frac{-22}{41} \\6 ( x + 1 ) - 4 ( y -1 ) = 2\\ \end{cases}$

<=> $\begin{cases} y = 19/41 \\6 ( x + 1 ) - 4 ( \frac{19}{41} - 1 ) = 2\\ \end{cases}$ = $\begin{cases} y = 19/41\\x = \frac{-42}{41} \\ \end{cases}$

Câu 3

$\begin{cases} 5 ( x - y ) - 3 ( 2x + 3y ) = 12\\3 ( x + 2y ) - 4 ( x + 2y ) = 5\\ \end{cases}$

<=> $\begin{cases} 5x - 5y - 6x - 9y = 12\\ - ( x + 2y ) = 5\\ \end{cases}$

<=> $\begin{cases} -x - 14y = 12\\-x + 2y = 5\\ \end{cases}$

<=> $\begin{cases} - 1by = 7\\- x + 2y = 5\\ \end{cases}$ <=> $\begin{cases} y = -7/16\\x = -47/8\\ \end{cases}$

Câu 5

$\begin{cases} \frac{x-y}{2} + \frac{x - 3y}{4} = 0\\\frac{3x - 5y + 1 }{2} - 1 = 0\\ \end{cases}$ <=> $\begin{cases} 2x - 2y + x - 3y = 0\\3x - 5y + 1 - 2 = 0\\ \end{cases}$

<=> $\begin{cases} 3x - 5y = 0\\3x - 5y - 1 = 0\\ \end{cases}$ => vô lí

=> hệ phương trình vô nghiệm

Câu 6: 

$\begin{cases} \frac{1}{2} ( x + 2 ) ( y - + 3 ) = \frac{1}{2} xy + 50 \\\frac{1}{2} ( x - 2 ) ( y - 2 ) = \frac{1}{2} xy = -32\\ \end{cases}$

<=> $\begin{cases} xy + 3x + 2y + 6 = xy + 100\\xy - 2x - 2y + 4 = xy - 64\\ \end{cases}$

<=> $\begin{cases} 3x + 2y = 94\\-2x - 2y = -68\\ \end{cases}$ <=> $\begin{cases} 3x + 2y = 94\\2x + 2y = 68\\ \end{cases}$

<=> $\begin{cases} 3x + 2y = 94\\x = 26\\ \end{cases}$ => $\begin{cases} 3.26 + 2.y = 94\\x = 26\\ \end{cases}$

<=> $\begin{cases} y = 8\\x = 26\\ \end{cases}$

Đáp án:

Đáp án: Câu 2

= {2(x+1)−15(y−1)=83(x+1)−2(y−1)=1{2(x+1)−15(y−1)=83(x+1)−2(y−1)=1

<=> {6(x+1)−45(y−1)=246(x+1)−4(y−1)=2{6(x+1)−45(y−1)=246(x+1)−4(y−1)=2

<=> {−41(y−1)=226(x+1)−4(y−1)=2{−41(y−1)=226(x+1)−4(y−1)=2 <=> {y−1=−22416(x+1)−4(y−1)=2{y−1=−22416(x+1)−4(y−1)=2

<=> {y=19/416(x+1)−4(1941−1)=2{y=19/416(x+1)−4(1941−1)=2 = {y=19/41x=−4241{y=19/41x=−4241

Câu 3

{5(x−y)−3(2x+3y)=123(x+2y)−4(x+2y)=5{5(x−y)−3(2x+3y)=123(x+2y)−4(x+2y)=5

<=> {5x−5y−6x−9y=12−(x+2y)=5{5x−5y−6x−9y=12−(x+2y)=5

<=> {−x−14y=12−x+2y=5{−x−14y=12−x+2y=5

<=> {−1by=7−x+2y=5{−1by=7−x+2y=5 <=> {y=−7/16x=−47/8{y=−7/16x=−47/8

Câu 5

{x−y2+x−3y4=03x−5y+12−1=0{x−y2+x−3y4=03x−5y+12−1=0 <=> {2x−2y+x−3y=03x−5y+1−2=0{2x−2y+x−3y=03x−5y+1−2=0

<=> {3x−5y=03x−5y−1=0{3x−5y=03x−5y−1=0 => vô lí

=> hệ phương trình vô nghiệm

Câu 6: 

{12(x+2)(y−+3)=12xy+5012(x−2)(y−2)=12xy=−32{12(x+2)(y−+3)=12xy+5012(x−2)(y−2)=12xy=−32

<=> {xy+3x+2y+6=xy+100xy−2x−2y+4=xy−64{xy+3x+2y+6=xy+100xy−2x−2y+4=xy−64

<=> {3x+2y=94−2x−2y=−68{3x+2y=94−2x−2y=−68 <=> {3x+2y=942x+2y=68{3x+2y=942x+2y=68

<=> {3x+2y=94x=26{3x+2y=94x=26 => {3.26+2.y=94x=26{3.26+2.y=94x=26

<=> {y=8x=26