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  • Which of the following pairs of linear equations has unique solution, no solution, or infinitely many solutions. In case there is a unique solution, find it by using cross multiplication method. (ii) 2x + y = 5 3x + 2y = 8

Q1.    Which of the following pairs of linear equations has unique solution, no solution, or infinitely many solutions. In case there is a unique solution, find it by using cross multiplication method.

                (ii)    \\2x + y = 5 \\ 3x + 2y = 8

Answers (1)

best_answer

Given, two equations,

\\2x + y = 5.........(1) \\ 3x + 2y = 8..........(2)

Comparing these equations with a_1x+b_1y+c_1=0\:and\:a_2x+b_2y+c_2=0, we get

\frac{a_1}{a_2}=\frac{2}{3}

\frac{b_1}{b_2}=\frac{1}{2}

\frac{c_1}{c_2}=\frac{5}{8}

As we can see, 

\frac{a_1}{a_2}\neq\frac{b_1}{b_2}\neq\frac{c_1}{c_2}

Hence, the pair of equations has exactly one solution.

By Cross multiplication method,

\frac{x}{b_1c_2-b_2c_1}=\frac{y}{c_1a_2-c_2a_1}=\frac{1}{a_1b_2-a_2b_1}

\frac{x}{(1)(-8)-(2)(-5)}=\frac{y}{(-5)(3)-(-8)(2)}=\frac{1}{(2)(2)-(3)(1)}

\frac{x}{-8+10}=\frac{y}{-15+16}=\frac{1}{4-3}

\frac{x}{2}=\frac{y}{1}=\frac{1}{1}

x=2,\:and\:y=1

Posted by

Pankaj Sanodiya

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