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If the system of equations 2x+3y=7 …

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If the system of equations 2x+3y=7 and 29x+(a+b)y=28 has infinitely many solutions, then find a relationship between a and b.
  • 1 answers

Sia ? 6 years, 6 months ago

The given system of equations may be written as
{tex}2x + 3y - 7 = 0{/tex}
{tex}2ax + ay + by - 28 = 0{/tex} {tex}\Rightarrow{/tex}{tex} 2ax + (a + b)y - 28 = 0{/tex}
This system of equations is of the form
{tex}a_1x + b_1y + c_1 = 0{/tex}
{tex}a_2x + b_2y + c_2 = 0{/tex}
where, a1 = 2, b1 = 3, c1 = -7
And, a2 = 2a, b2 = a + b, c2 = -28
For the system of equations to have infinite solutions,
{tex}\frac{{{a_1}}}{{{a_2}}} = \frac{{{b_1}}}{{{b_2}}} = \frac{{{c_1}}}{{{c_2}}}{/tex}
{tex} \Rightarrow \frac{2}{{2a}} = \frac{3}{{a + b}} = \frac{{ - 7}}{{ - 28}}{/tex}
{tex}\Rightarrow \frac{1}{a} = \frac{3}{{a + b}} = \frac{1}{4}{/tex}
Now, {tex}\frac{1}{a} = \frac{1}{4}{/tex}
{tex}\Rightarrow{/tex} a = 4
And, {tex}\frac{1}{a} = \frac{3}{{a + b}}{/tex}
{tex}\Rightarrow{/tex}{tex} a + b = 3a{/tex}
{tex}\Rightarrow{/tex} {tex}2a = b{/tex}
{tex}\Rightarrow{/tex} 2 {tex}\times{/tex} 4 = b
{tex}\Rightarrow{/tex}{tex} b = 8{/tex}
Hence, the given system of equations will have infinite number of solutions for {tex}a = 4\ and\ b = 8.{/tex}

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