Question 7 of 9beginner💡 UnderstandShort Answer5 marks

On comparing the ratios a1a2,b1b2\frac{a_1}{a_2}, \frac{b_1}{b_2} and c1c2\frac{c_1}{c_2}, find out whether the following pair of linear equations are consistent, or inconsistent.

(i)

3x+2y=53x + 2y = 5; 2x3y=72x - 3y = 7

Answer

Comparing the equations 3x+2y=53x + 2y = 5 and 2x3y=72x - 3y = 7 with standard form, we get a1=3,b1=2,c1=5a_1 = 3, b_1 = 2, c_1 = -5 and a2=2,b2=3,c2=7a_2 = 2, b_2 = -3, c_2 = -7. Calculating the ratios: a1a2=32\frac{a_1}{a_2} = \frac{3}{2} and b1b2=23\frac{b_1}{b_2} = \frac{2}{-3}. Since a1a2b1b2\frac{a_1}{a_2} \neq \frac{b_1}{b_2}, the lines intersect at a point. Thus, the pair of equations is consistent.

(ii)

2x3y=82x - 3y = 8; 4x6y=94x - 6y = 9

Answer

Comparing the equations 2x3y=82x - 3y = 8 and 4x6y=94x - 6y = 9, we get a1=2,b1=3,c1=8a_1 = 2, b_1 = -3, c_1 = -8 and a2=4,b2=6,c2=9a_2 = 4, b_2 = -6, c_2 = -9. Calculating the ratios: a1a2=24=12\frac{a_1}{a_2} = \frac{2}{4} = \frac{1}{2}, b1b2=36=12\frac{b_1}{b_2} = \frac{-3}{-6} = \frac{1}{2}, and c1c2=89=89\frac{c_1}{c_2} = \frac{-8}{-9} = \frac{8}{9}. Since a1a2=b1b2c1c2\frac{a_1}{a_2} = \frac{b_1}{b_2} \neq \frac{c_1}{c_2}, the lines are parallel. Thus, the pair of equations is inconsistent.

(iii)

32x+53y=7\frac{3}{2}x + \frac{5}{3}y = 7; 9x10y=149x - 10y = 14

Answer

Comparing the equations 32x+53y=7\frac{3}{2}x + \frac{5}{3}y = 7 and 9x10y=149x - 10y = 14, we get a1=32,b1=53,c1=7a_1 = \frac{3}{2}, b_1 = \frac{5}{3}, c_1 = -7 and a2=9,b2=10,c2=14a_2 = 9, b_2 = -10, c_2 = -14. Calculating the ratios: a1a2=3/29=16\frac{a_1}{a_2} = \frac{3/2}{9} = \frac{1}{6} and b1b2=5/310=16\frac{b_1}{b_2} = \frac{5/3}{-10} = -\frac{1}{6}. Since a1a2b1b2\frac{a_1}{a_2} \neq \frac{b_1}{b_2}, the lines intersect. Thus, the pair of equations is consistent.

(iv)

5x3y=115x - 3y = 11; 10x+6y=22-10x + 6y = -22

Answer

Comparing the equations 5x3y=115x - 3y = 11 and 10x+6y=22-10x + 6y = -22, we get a1=5,b1=3,c1=11a_1 = 5, b_1 = -3, c_1 = -11 and a2=10,b2=6,c2=22a_2 = -10, b_2 = 6, c_2 = 22. Calculating the ratios: a1a2=510=12\frac{a_1}{a_2} = \frac{5}{-10} = -\frac{1}{2}, b1b2=36=12\frac{b_1}{b_2} = \frac{-3}{6} = -\frac{1}{2}, and c1c2=1122=12\frac{c_1}{c_2} = \frac{-11}{22} = -\frac{1}{2}. Since a1a2=b1b2=c1c2\frac{a_1}{a_2} = \frac{b_1}{b_2} = \frac{c_1}{c_2}, the lines are coincident. Thus, the pair of equations is consistent.

(v)

43x+2y=8\frac{4}{3}x + 2y = 8; 2x+3y=122x + 3y = 12

Answer

Comparing the equations 43x+2y=8\frac{4}{3}x + 2y = 8 and 2x+3y=122x + 3y = 12, we get a1=43,b1=2,c1=8a_1 = \frac{4}{3}, b_1 = 2, c_1 = -8 and a2=2,b2=3,c2=12a_2 = 2, b_2 = 3, c_2 = -12. Calculating the ratios: a1a2=4/32=23\frac{a_1}{a_2} = \frac{4/3}{2} = \frac{2}{3}, b1b2=23\frac{b_1}{b_2} = \frac{2}{3}, and c1c2=812=23\frac{c_1}{c_2} = \frac{-8}{-12} = \frac{2}{3}. Since a1a2=b1b2=c1c2\frac{a_1}{a_2} = \frac{b_1}{b_2} = \frac{c_1}{c_2}, the lines are coincident. Thus, the pair of equations is consistent.

Explanation

The textbook context outlines three conditions for consistency based on comparing ratios of coefficients. If a1a2b1b2\frac{a_1}{a_2} \neq \frac{b_1}{b_2}, the lines intersect and the system is consistent with a unique solution. If a1a2=b1b2c1c2\frac{a_1}{a_2} = \frac{b_1}{b_2} \neq \frac{c_1}{c_2}, the lines are parallel and the system is inconsistent with no solution. If a1a2=b1b2=c1c2\frac{a_1}{a_2} = \frac{b_1}{b_2} = \frac{c_1}{c_2}, the lines are coincident and the system is dependent and consistent with infinitely many solutions. Each part of the question is solved by identifying coefficients and calculating these ratios to classify the system.