Equation of a line with slope 3 through point (17,21)

Geometry Level 1

What is the value of b b in the equation y = 3 x + b y = 3x + b , given that the line passes through the point ( 17 , 21 ) (17,21) ?


The answer is -30.

John Faucett by John Faucett , 26, Germany

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2 solutions

John Faucett
Jul 27, 2019

This problem can be solved algebraically.

  1. y = 3 x + b y = 3x + b
  2. 21 = 3 ( 17 ) + b 21 = 3(17) + b
  3. 21 = 51 + b 21 = 51 + b
  4. − 30 = b -30 = b
2 Helpful 0 Interesting 0 Brilliant 0 Confused

We have the point ( 17 , 21 ) \left( 17, 21 \right) so then 21 = 3 ( 20 − 3 ) + b 21 = 3\left( 20 - 3 \right) + b we know 60 − 9 = 51 60 - 9 = 51 and so we know b = − 30 \boxed{b= -30}

1 Helpful 0 Interesting 0 Brilliant 0 Confused

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