Q9 / 109 · NTA Abhyas (JEE Main) 2020 · Mathematics · Straight Lines

If 5a+4b+20c=t, then the value of t for which the line ax+by+c-1=0 always passes through a fixed point is

  • A
    0
  • Correct answer
    B
    20
  • C
    30
  • D
    None of these

Solution

Equation of the given line is ax+by+c−1=0

⇒20 ax+20 by+20 c−20=0     .....(i)

From the given relation, substituting value of c, we get,
20 ax+20 by+t−5a−4b−20=0

⇒20 a( x− 1 4 )+20 b( y− 1 5 )+( t−20 )=0

Clearly for t=20, the given line will pass through the point ( 1 4 , 1 5 ) for all the values of a & b

Hence, the correct answer is option: 'B'.

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