Intermediate Geometry : How to find out if a point is on a line with an equation

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #11 : Other Lines

Which of the following points is on the line \(\displaystyle y=6x-5\)

Possible Answers:

None of these

\(\displaystyle (-4,3)\)

\(\displaystyle (-3,4)\)

\(\displaystyle (7,2)\)

\(\displaystyle (2,7)\)

Correct answer:

\(\displaystyle (2,7)\)

Explanation:

To ascertain if a point is on a line we must plug that coordinate pair into the equation of the line. If a true statement such as 5=5 is returned then we know that point is on our line. 

\(\displaystyle y=6x-5\)

Choose the point you suspect is on the line.

\(\displaystyle (2,7)\)

\(\displaystyle 7=6(2)-5\)

\(\displaystyle 7=7\)

Since the equation returned a true statement the point \(\displaystyle \mathbf{(2,7)}\) is on our line.

Example Question #12 : Other Lines

Which of the following points is found on the line \(\displaystyle y=-2x+12\)?

Possible Answers:

\(\displaystyle (12, -22)\)

\(\displaystyle (16, -20)\)

\(\displaystyle (18, -26)\)

\(\displaystyle (-20, 10)\)

Correct answer:

\(\displaystyle (16, -20)\)

Explanation:

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=16\) into the given equation will give the following:

\(\displaystyle y=-2x+12\)

\(\displaystyle y=-2(16)+12=-32+12=-20\)

Thus, \(\displaystyle (16, -20)\) is on the line.

Example Question #13 : Other Lines

Which of the following points is found on the line \(\displaystyle y=\frac{1}{6}x+5\)?

Possible Answers:

\(\displaystyle (24, 9)\)

\(\displaystyle (12, -3)\)

\(\displaystyle (18, 2)\)

\(\displaystyle (60, 55)\)

Correct answer:

\(\displaystyle (24, 9)\)

Explanation:

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=24\) into the given equation will give the following:

\(\displaystyle y=\frac{1}{6}x+5\)

\(\displaystyle y=\frac{1}{6}(24)+5=4+5=9\)

Thus, \(\displaystyle (24, 9)\) is on the line.

Example Question #14 : Other Lines

Which of the following points is found on the line \(\displaystyle y=-10x+8\)?

Possible Answers:

\(\displaystyle (20, 208)\)

\(\displaystyle (-1, 2)\)

\(\displaystyle (5, -58)\)

\(\displaystyle (10, -92)\)

Correct answer:

\(\displaystyle (10, -92)\)

Explanation:

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=10\) into the given equation will give the following:

\(\displaystyle y=-10x+8\)

\(\displaystyle y=-10(10)+8=-100+8=-92\)

Thus, \(\displaystyle (10, -92)\) is on the line.

Example Question #11 : Other Lines

Which of the following points is found on the line \(\displaystyle y=13x-11\)?

Possible Answers:

\(\displaystyle (-10, 141)\)

\(\displaystyle (2, 20)\)

\(\displaystyle (1, 2)\)

\(\displaystyle (13, 169)\)

Correct answer:

\(\displaystyle (1, 2)\)

Explanation:

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=1\) into the given equation will give the following:

\(\displaystyle y=13x-11\)

\(\displaystyle y=13(1)-11=13-11=2\)

Thus, \(\displaystyle (1, 2)\) is on the line.

Example Question #16 : Other Lines

Which of the following points is found on the line \(\displaystyle y=-\frac{3}{2}x+10\)?

Possible Answers:

\(\displaystyle (6, 19)\)

\(\displaystyle (12, 28)\)

\(\displaystyle (-8, 6)\)

\(\displaystyle (-10, 25)\)

Correct answer:

\(\displaystyle (-10, 25)\)

Explanation:

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=-10\) into the given equation will give the following:

\(\displaystyle y=-\frac{3}{2}x+10\)

\(\displaystyle y=-\frac{3}{2}(-10)+10=15+10=25\)

Thus, \(\displaystyle (-10, 25)\) is on the line.

Example Question #12 : Other Lines

Which of the following points is found on the line \(\displaystyle y=\frac{1}{5}x-5\)?

Possible Answers:

\(\displaystyle (-20, -9)\)

\(\displaystyle (12, 14)\)

\(\displaystyle (2, -\frac{4}{5})\)

\(\displaystyle (-1, \frac{4}{5})\)

Correct answer:

\(\displaystyle (-20, -9)\)

Explanation:

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=-20\) into the given equation will give the following:

\(\displaystyle y=\frac{1}{5}x-5\)

\(\displaystyle y=\frac{1}{5}(-20)-5=-4-5=-9\)

Thus, \(\displaystyle (-20, -9)\) is on the line.

Example Question #18 : Other Lines

Which of the following points is found on the line \(\displaystyle 3x+4y=5\)?

Possible Answers:

\(\displaystyle (-1, 12)\)

\(\displaystyle (0, -\frac{3}{4})\)

\(\displaystyle (2, -\frac{1}{2})\)

\(\displaystyle (12, -\frac{31}{4})\)

Correct answer:

\(\displaystyle (12, -\frac{31}{4})\)

Explanation:

Start by rewriting the equation into slope-intercept form.

\(\displaystyle 3x+4y=5\)

\(\displaystyle 4y=-3x+5\)

\(\displaystyle y=-\frac{3}{4}x+\frac{5}{4}\)

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=12\) into the given equation will give the following:

\(\displaystyle y=-\frac{3}{4}x+\frac{5}{4}\)

\(\displaystyle y=-\frac{3}{4}(12)+\frac{5}{4}=-9+\frac{5}{4}=-\frac{31}{4}\)

Thus, \(\displaystyle (12, -\frac{31}{4})\) is on the line.

Example Question #19 : Other Lines

Which of the following points is on the line \(\displaystyle 12x-4y=18\)?

Possible Answers:

\(\displaystyle (-13, -\frac{87}{2})\)

\(\displaystyle (\frac{3}{2}, 1)\)

\(\displaystyle (-\frac{1}{2}, 6)\)

\(\displaystyle (14, \frac{41}{2})\)

Correct answer:

\(\displaystyle (-13, -\frac{87}{2})\)

Explanation:

Start by rewriting the equation into slope-intercept form.

\(\displaystyle 12x-4y=18\)

\(\displaystyle -4y=-12x+18\)

\(\displaystyle y=3x-\frac{9}{2}\)

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=-13\) into the given equation will give the following:

\(\displaystyle y=3x-\frac{9}{2}\)

\(\displaystyle y=3(-13)-\frac{9}{2}=-39-\frac{9}{2}=-\frac{87}{2}\)

Thus, \(\displaystyle (-13, -\frac{87}{2})\) is on the line.

Example Question #20 : Other Lines

Which of the following points is found on the line \(\displaystyle 5y+10x=20\)?

Possible Answers:

\(\displaystyle (-7, 18)\)

\(\displaystyle (8, 12)\)

\(\displaystyle (\frac{1}{2}, -3)\)

\(\displaystyle (10, 9)\)

Correct answer:

\(\displaystyle (-7, 18)\)

Explanation:

Start by rewriting the equation into slope-intercept form.

\(\displaystyle 5y+10x=20\)

\(\displaystyle 5y=-10x+20\)

\(\displaystyle y=-2x+4\)

To find which point is on the line, take the \(\displaystyle x\)-coordinate, and plug it into the given equation to solve for \(\displaystyle y\). If the \(\displaystyle y\)-value matches the \(\displaystyle y\)-coordinate of the same point, then the point is on the line.

Plugging in \(\displaystyle x=-7\) into the given equation will give the following:

\(\displaystyle y=-2x+4\)

\(\displaystyle y=-2(-7)+4=18\)

Thus, \(\displaystyle (-7, 18)\) is on the line.

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