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Mathematics

Solve the following pair of (simultaneous) equations using method of elimination by substitution :

3x25y3+2=0\dfrac{3x}{2} - \dfrac{5y}{3} + 2 = 0

x3+y2=216\dfrac{x}{3} + \dfrac{y}{2} = 2\dfrac{1}{6}

Linear Equations

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Answer

Given,

Equations : 3x25y3+2=0,x3+y2=216\dfrac{3x}{2} - \dfrac{5y}{3} + 2 = 0, \dfrac{x}{3} + \dfrac{y}{2} = 2\dfrac{1}{6}

3x25y3+2=09x10y+126=09x10y+12=010y=9x+12y=9x+1210.......(1)\Rightarrow \dfrac{3x}{2} - \dfrac{5y}{3} + 2 = 0 \\[1em] \Rightarrow \dfrac{9x - 10y + 12}{6} = 0 \\[1em] \Rightarrow 9x - 10y + 12 = 0 \\[1em] \Rightarrow 10y = 9x + 12 \\[1em] \Rightarrow y = \dfrac{9x + 12}{10} …….(1)

Substituting value of y from equation (1) in x3+y2=216\dfrac{x}{3} + \dfrac{y}{2} = 2\dfrac{1}{6}, we get :

x3+9x+12102=216x3+9x+1220=13620x+3(9x+12)60=13620x+27x+3660=13647x+3660=13647x+36=136×6047x+36=13047x=94x=9447=2.\Rightarrow \dfrac{x}{3} + \dfrac{\dfrac{9x + 12}{10}}{2} = 2\dfrac{1}{6} \\[1em] \Rightarrow \dfrac{x}{3} + \dfrac{9x + 12}{20} = \dfrac{13}{6} \\[1em] \Rightarrow \dfrac{20x + 3(9x + 12)}{60} = \dfrac{13}{6} \\[1em] \Rightarrow \dfrac{20x + 27x + 36}{60} = \dfrac{13}{6} \\[1em] \Rightarrow \dfrac{47x + 36}{60} = \dfrac{13}{6} \\[1em] \Rightarrow 47x + 36 = \dfrac{13}{6} \times 60 \\[1em] \Rightarrow 47x + 36 = 130 \\[1em] \Rightarrow 47x = 94 \\[1em] \Rightarrow x = \dfrac{94}{47} = 2.

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

y=9x+1210y=9×2+1210y=18+1210y=3010=3.\Rightarrow y = \dfrac{9x + 12}{10} \\[1em] \Rightarrow y = \dfrac{9 \times 2 + 12}{10} \\[1em] \Rightarrow y = \dfrac{18 + 12}{10} \\[1em] \Rightarrow y = \dfrac{30}{10} = 3.

Hence, x = 2 and y = 3.

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