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Mathematics

Solve the following simultaneous equations:

x+y82=x+2y143=3x+y1211\dfrac{x + y - 8}{2} = \dfrac{x + 2y - 14}{3} = \dfrac{3x + y - 12}{11}

Linear Equations

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Answer

Given,

x+y82=x+2y143=3x+y1211\dfrac{x + y - 8}{2} = \dfrac{x + 2y - 14}{3} = \dfrac{3x + y - 12}{11}

Solving L.H.S. of the given equation,

x+y82=x+2y1433(x+y8)=2(x+2y14)3x+3y24=2x+4y283x+3y2x4y=28+24xy=4x=4+y ….(1)\Rightarrow \dfrac{x + y - 8}{2} = \dfrac{x + 2y - 14}{3} \\[1em] \Rightarrow 3(x + y - 8) = 2(x + 2y - 14) \\[1em] \Rightarrow 3x + 3y - 24 = 2x + 4y - 28 \\[1em] \Rightarrow 3x + 3y - 2x - 4y = -28 + 24 \\[1em] \Rightarrow x - y = -4 \\[1em] \Rightarrow x = -4 + y \text{ ….(1)}

Solving R.H.S. of the given equation,

x+2y143=3x+y121111(x+2y14)=3(3x+y12)11x+22y154=9x+3y3611x+22y9x3y=36+1542x+19y=118 ……..(2)\Rightarrow \dfrac{x + 2y - 14}{3} = \dfrac{3x + y - 12}{11} \\[1em] \Rightarrow 11(x + 2y - 14) = 3(3x + y - 12) \\[1em] \Rightarrow 11x + 22y - 154 = 9x + 3y - 36 \\[1em] \Rightarrow 11x + 22y - 9x - 3y = -36 + 154 \\[1em] \Rightarrow 2x + 19y = 118 \text{ ……..(2)}

Substituting value of x from equation (1) in (2), we get :

⇒ 2(-4 + y) + 19y = 118

⇒ -8 + 2y + 19y = 118

⇒ 21y = 118 + 8

⇒ 21y = 126

⇒ y = 12621=6\dfrac{126}{21} = 6.

Substituting value of y in equation (1), we get :

⇒ x = -4 + y

⇒ x = -4 + 6

⇒ x = 2.

Hence, x = 2, y = 6.

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