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Q3(iii):
On comparing the ratios $\frac{a_1}{a_2}$, $\frac{b_1}{b_2}$, and $\frac{c_1}{c_2}$, find out whether the following pair of linear equations are consistent, or inconsistent. (iii) $\frac{3}{2}x + \frac{5}{3}y = 7$ ; 9x – 10y = 14

Solution :

Given: A pair of linear equations in two variables:

Equation 1: $\frac{3}{2}x + \frac{5}{3}y = 7$

Equation 2: $9x - 10y = 14$

To Find: Determine whether the given pair of linear equations is consistent or inconsistent by comparing the ratios $\frac{a_1}{a_2}$, $\frac{b_1}{b_2}$, and $\frac{c_1}{c_2}$.

Step 1: Standardizing the Equations

A linear equation in two variables is represented in the standard form $ax + by + c = 0$ or $ax + by = c$. We will write both equations in the form $a_1x + b_1y = c_1$ and $a_2x + b_2y = c_2$.

Equation 1: $\frac{3}{2}x + \frac{5}{3}y = 7$

Equation 2: $9x - 10y = 14$

Step 2: Identifying Coefficients

Comparing the given equations with $a_1x + b_1y = c_1$ and $a_2x + b_2y = c_2$:

For Equation 1: $a_1 = \frac{3}{2}$, $b_1 = \frac{5}{3}$, $c_1 = 7$

For Equation 2: $a_2 = 9$, $b_2 = -10$, $c_2 = 14$

Step 3: Calculating the Ratios

Now, we calculate the ratios of the coefficients:

Ratio of $x$-coefficients: $\frac{a_1}{a_2} = \frac{3/2}{9} = \frac{3}{2 \times 9} = \frac{3}{18} = \frac{1}{6}$

Ratio of $y$-coefficients: $\frac{b_1}{b_2} = \frac{5/3}{-10} = \frac{5}{3 \times (-10)} = \frac{5}{-30} = -\frac{1}{6}$

Ratio of constants: $\frac{c_1}{c_2} = \frac{7}{14} = \frac{1}{2}$

Step 4: Comparing the Ratios

We observe the values obtained:

$\frac{a_1}{a_2} = \frac{1}{6}$

$\frac{b_1}{b_2} = -\frac{1}{6}$

Since $\frac{1}{6} \neq -\frac{1}{6}$, it follows that $\frac{a_1}{a_2} \neq \frac{b_1}{b_2}$.

Step 5: Applying the Consistency Condition

[Theorem: For a pair of linear equations $a_1x + b_1y + c_1 = 0$ and $a_2x + b_2y + c_2 = 0$, if $\frac{a_1}{a_2} \neq \frac{b_1}{b_2}$, the lines intersect at a unique point and the system is consistent.]

Because the condition $\frac{a_1}{a_2} \neq \frac{b_1}{b_2}$ is satisfied, the pair of linear equations has a unique solution.

Final Answer: The pair of linear equations is consistent.


More Questions from Class 10 Mathematics Pair of linear equations in two variable EXERCISE 3.1


CBSE Solutions for Class 10 Mathematics Pair of linear equations in two variable


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