Straight lines Worked Solutions — A-Level Maths

Fully worked, step-by-step solutions to A-Level Straight lines questions. See exactly how to solve problems on gradient, coordinate geometry, midpoint, distance.

gradientcoordinate geometrymidpointdistancePythagorasequation of a line
A-Level70 questionsStep-by-step solutions
Question 1
3 markseasy
Find the gradient of the line joining the points A(1, 2)A\left(1,\ 2\right) and B(4, 11)B\left(4,\ 11\right).

Worked solution

  1. Write down the two points

    A(1, 2),B(4, 11)A\left(1,\ 2\right),\quad B\left(4,\ 11\right)

    Label the first point (x_1, y_1) and the second (x_2, y_2). Keeping them in order stops sign mistakes later.

  2. Recall the gradient formula

    m=y2y1x2x1m=\frac{y_2-y_1}{x_2-x_1}

    The gradient measures steepness: how much the line goes up (or down) for each step to the right. This is the change in y divided by the change in x.

  3. Substitute the coordinates

    m=11(2)4(1)m=\frac{11-(2)}{4-(1)}

    Carefully put each number in its place. Subtracting a negative becomes adding, so watch those double signs.

  4. Simplify to find the gradient

    m=3m=3

    Work out the top and bottom, then simplify the fraction. A positive answer slopes uphill, a negative one slopes downhill.

Answer
33
Question 2
3 markseasy
Find the gradient of the line joining the points A(2, 5)A\left(-2,\ 5\right) and B(3, 5)B\left(3,\ -5\right).

Worked solution

  1. Write down the two points

    A(2, 5),B(3, 5)A\left(-2,\ 5\right),\quad B\left(3,\ -5\right)

    Label the first point (x_1, y_1) and the second (x_2, y_2). Keeping them in order stops sign mistakes later.

  2. Recall the gradient formula

    m=y2y1x2x1m=\frac{y_2-y_1}{x_2-x_1}

    The gradient measures steepness: how much the line goes up (or down) for each step to the right. This is the change in y divided by the change in x.

  3. Substitute the coordinates

    m=5(5)3(2)m=\frac{-5-(5)}{3-(-2)}

    Carefully put each number in its place. Subtracting a negative becomes adding, so watch those double signs.

  4. Simplify to find the gradient

    m=2m=-2

    Work out the top and bottom, then simplify the fraction. A positive answer slopes uphill, a negative one slopes downhill.

Answer
2-2
Question 3
3 markseasy
Find the gradient of the line joining the points A(3, 1)A\left(-3,\ -1\right) and B(2, 4)B\left(2,\ 4\right).

Worked solution

  1. Write down the two points

    A(3, 1),B(2, 4)A\left(-3,\ -1\right),\quad B\left(2,\ 4\right)

    Label the first point (x_1, y_1) and the second (x_2, y_2). Keeping them in order stops sign mistakes later.

  2. Recall the gradient formula

    m=y2y1x2x1m=\frac{y_2-y_1}{x_2-x_1}

    The gradient measures steepness: how much the line goes up (or down) for each step to the right. This is the change in y divided by the change in x.

  3. Substitute the coordinates

    m=4(1)2(3)m=\frac{4-(-1)}{2-(-3)}

    Carefully put each number in its place. Subtracting a negative becomes adding, so watch those double signs.

  4. Simplify to find the gradient

    m=1m=1

    Work out the top and bottom, then simplify the fraction. A positive answer slopes uphill, a negative one slopes downhill.

Answer
11
Question 4
2 markseasy
Find the midpoint of the line segment joining A(2, 3)A\left(2,\ 3\right) and B(8, 7)B\left(8,\ 7\right).

Worked solution

  1. Recall the midpoint formula

    M=(x1+x22, y1+y22)M=\left(\frac{x_1+x_2}{2},\ \frac{y_1+y_2}{2}\right)

    The midpoint is exactly halfway along the line segment. We simply average the x-values and average the y-values.

  2. Substitute the x-coordinates

    2+82=5\frac{2+8}{2}=5

    Add the two x-values together and split the result in half. This gives the x-coordinate of the middle point.

  3. Substitute the y-coordinates

    3+72=5\frac{3+7}{2}=5

    Do the same with the y-values. Adding then halving finds the height of the middle point.

  4. State the midpoint

    M=(5, 5)M=\left(5,\ 5\right)

    Put the two answers together as a coordinate. That point sits dead centre between A and B.

Answer
(5, 5)\left(5,\ 5\right)
Question 5
2 markseasy
Find the midpoint of the line segment joining A(4, 1)A\left(-4,\ 1\right) and B(6, 3)B\left(6,\ -3\right).

Worked solution

  1. Recall the midpoint formula

    M=(x1+x22, y1+y22)M=\left(\frac{x_1+x_2}{2},\ \frac{y_1+y_2}{2}\right)

    The midpoint is exactly halfway along the line segment. We simply average the x-values and average the y-values.

  2. Substitute the x-coordinates

    4+62=1\frac{-4+6}{2}=1

    Add the two x-values together and split the result in half. This gives the x-coordinate of the middle point.

  3. Substitute the y-coordinates

    1+32=1\frac{1+-3}{2}=-1

    Do the same with the y-values. Adding then halving finds the height of the middle point.

  4. State the midpoint

    M=(1, 1)M=\left(1,\ -1\right)

    Put the two answers together as a coordinate. That point sits dead centre between A and B.

Answer
(1, 1)\left(1,\ -1\right)

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