Give the equation of a line that goes through the point ( 4 , 9 ) and is parallel to the line − 3 x + 7 y = 21 .

Respuesta :

Esther

Answer:

[tex]\sf y=\dfrac{3}{7}x+\dfrac{51}{7}[/tex]

Step-by-step explanation:

Given equation: -3x + 7y = 21

Slope-Intercept Form: y = mx + b -

where:

  • m is the slope
  • b is the y-intercept (when x = 0)

Note: parallel lines have the same slope.

1. Rewrite the given equation in slope-intercept form:

[tex]\sf -3x + 7y = 21\ \textsf{[add 3x to both sides]}\\\\-3x + 3x + 7y = 21 + 3x\\\\7y = 3x + 21\ \textsf{[divide both sides by 7]}\\\\\dfrac{7y}{7}=\dfrac{3x+21}{7}\\\\\implies y=\dfrac{3}{7}x+3[/tex]

Here, this equation has a slope of ³⁄₇ and a y-intercept of 3.

2. Find the equation of the parallel line:

substitute the point (4, 9) into the equation to find the value of b

[tex]\sf y=\dfrac{3}{7}x+b\\\\9=\dfrac{3}{7}(4)+b\\\\9=\dfrac{12}{7}+b\\\\\dfrac{63}{7}-\dfrac{12}{7}=\dfrac{12}{7}-\dfrac{12}{7}+b\\\\\dfrac{51}{7}=b[/tex]

[tex]\sf \textsf{Equation:}\ y=\dfrac{3}{7}x+\dfrac{51}{7}[/tex]

3. Check your work:

[tex]\sf y=\dfrac{3}{7}x+\dfrac{51}{7}\\\\9=\dfrac{3}{7}(4)+\dfrac{51}{7}\\\\9=\dfrac{12}{7}+\dfrac{51}{7}\\\\9=\dfrac{63}{7}\\\\9=9\ \checkmark[/tex]

[tex]\sf \textsf{Therefore, the equation of the parallel line is:}\ y=\dfrac{3}{7}x+\dfrac{51}{7}[/tex]

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