KnowledgeBoat Logo
|

Mathematics

Solve the following system of equations by using the method of cross multiplication:

5x+12y1=12,10x+1+2y1=52\dfrac{5}{x + 1} - \dfrac{2}{y - 1} = \dfrac{1}{2},\dfrac{10}{x + 1} + \dfrac{2}{y - 1} = \dfrac{5}{2}, where x ≠ -1 and x ≠ 1.

Linear Equations

2 Likes

Answer

5x+12y1=12,10x+1+2y1=52\dfrac{5}{x + 1} - \dfrac{2}{y - 1} = \dfrac{1}{2},\dfrac{10}{x + 1} + \dfrac{2}{y - 1} = \dfrac{5}{2}

Substituting 1x+1=u,1y1=v\dfrac{1}{x + 1}= u, \dfrac{1}{y - 1} = v in 5x+12y1=12\dfrac{5}{x + 1} - \dfrac{2}{y - 1} = \dfrac{1}{2}, we get:

⇒ 5u - 2v = 12\dfrac{1}{2}

⇒ 5u - 2v - 12\dfrac{1}{2} = 0     ….(1)

Substituting 1x+1=u,1y1=v\dfrac{1}{x + 1}= u, \dfrac{1}{y - 1} = v in 10x+1+2y1=52\dfrac{10}{x + 1} + \dfrac{2}{y - 1} = \dfrac{5}{2}, we get:

⇒ 10u + 2v = 52\dfrac{5}{2}

⇒ 10u + 2v - 52\dfrac{5}{2} = 0     ….(2)

Multiply equation (1) and (2) by 2, we get,

2(5u2v12)2\Big(5u - 2v - \dfrac{1}{2}\Big)= 0

⇒ 10u - 4v - 1 = 0     …….(3)

2(10u+2v52)2\Big(10u + 2v - \dfrac{5}{2}\Big) = 0

⇒ 20u + 4v - 5 = 0     ………(4)

Applying cross-multiplication method for solving equations (3) and (4), we get :

Solve the following system of equations by using the method of cross multiplication: R.S. Aggarwal Mathematics Solutions ICSE Class 9.

u(4)×(5)(4)×(1)=v(1)×(20)(5)×(10)=1(10)×(4)(20)×(4)u(20)+4=v20+50=140+80u24=v30=1120u24=1120 and v30=1120u=24120 and v=30120u=15 and v=14.\Rightarrow \dfrac{u}{(-4) \times (-5) - (4) \times (-1)} = \dfrac{v}{(-1) \times (20) - (-5) \times (10)} = \dfrac{1}{(10) \times (4) - (20) \times (-4)} \\[1em] \Rightarrow \dfrac{u}{(20) + 4} = \dfrac{v}{-20 + 50} = \dfrac{1}{40 + 80} \\[1em] \Rightarrow \dfrac{u}{24} = \dfrac{v}{30} = \dfrac{1}{120} \\[1em] \Rightarrow \dfrac{u}{24} = \dfrac{1}{120} \text{ and } \dfrac{v}{30} = \dfrac{1}{120} \\[1em] \Rightarrow u = \dfrac{24}{120} \text{ and } v = \dfrac{30}{120} \\[1em] \Rightarrow u = \dfrac{1}{5} \text{ and } v = \dfrac{1}{4}.

Now we have u = 15 and v=14\dfrac{1}{5} \text{ and } v = \dfrac{1}{4},

1x+1=u1x+1=15x+1=5x=51=41y1=v1y1=14y1=4y=4+1=5.\Rightarrow \dfrac{1}{x + 1} = u \\[1em] \Rightarrow \dfrac{1}{x + 1} = \dfrac{1}{5} \\[1em] \Rightarrow x + 1 = 5 \\[1em] \Rightarrow x = 5 - 1 = 4 \\[1em] \Rightarrow \dfrac{1}{y - 1} = v \\[1em] \Rightarrow \dfrac{1}{y - 1} = \dfrac{1}{4} \\[1em] \Rightarrow y - 1 = 4 \\[1em] \Rightarrow y = 4 + 1 = 5.

Hence, x = 4, y = 5.

Answered By

1 Like


Related Questions