Find the Midpoint of (-2, 3) and (4, -1) — Midpoint Formula

easy CBSE NCERT Class 10 Chapter 7 3 min read

Question

Find the midpoint of the line segment joining the points (2,3)(-2, 3) and (4,1)(4, -1).

Solution — Step by Step

The midpoint MM of a segment joining (x1,y1)(x_1, y_1) and (x2,y2)(x_2, y_2) is:

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

This is just the average of the x-coordinates and the average of the y-coordinates — nothing more.

Let (x1,y1)=(2,3)(x_1, y_1) = (-2, 3) and (x2,y2)=(4,1)(x_2, y_2) = (4, -1).

Labelling first prevents sign errors, which is where most marks are lost in board exams.

xM=x1+x22=2+42=22=1x_M = \frac{x_1 + x_2}{2} = \frac{-2 + 4}{2} = \frac{2}{2} = 1 yM=y1+y22=3+(1)2=22=1y_M = \frac{y_1 + y_2}{2} = \frac{3 + (-1)}{2} = \frac{2}{2} = 1

The midpoint of the segment is M = (1, 1).

Why This Works

The midpoint formula is really just the arithmetic mean applied to coordinates. If you have two values on a number line, their average gives the point exactly halfway between them. We apply that idea separately to x and y.

Geometrically, you can verify: the distance from (2,3)(-2, 3) to (1,1)(1, 1) equals the distance from (1,1)(1, 1) to (4,1)(4, -1). Both come out to 13\sqrt{13}, confirming (1,1)(1, 1) sits exactly in the middle.

This question has appeared in NCERT Exercise 7.2 and is a guaranteed 2-marker in CBSE Class 10 boards. The formula is also the foundation for Section Formula questions — get comfortable with this before moving there.

Alternative Method

You can verify the midpoint by checking equal distances using the distance formula.

Distance from (2,3)(-2, 3) to (1,1)(1, 1):

d1=(1(2))2+(13)2=9+4=13d_1 = \sqrt{(1-(-2))^2 + (1-3)^2} = \sqrt{9 + 4} = \sqrt{13}

Distance from (1,1)(1, 1) to (4,1)(4, -1):

d2=(41)2+(11)2=9+4=13d_2 = \sqrt{(4-1)^2 + (-1-1)^2} = \sqrt{9 + 4} = \sqrt{13}

Since d1=d2d_1 = d_2, the point (1,1)(1, 1) divides the segment equally — confirmed as the midpoint. In exams, skip this verification unless explicitly asked.

Common Mistake

Students write 2+42=62=3\frac{-2 + 4}{2} = \frac{-6}{2} = -3 — treating 2+4-2 + 4 as 2×4=8-2 \times 4 = -8, or misreading it as (2+4)-(2+4). The negation applies only to the 2, not to the sum. Always compute the numerator first before dividing: 2+4=+2-2 + 4 = +2, then 22=1\frac{2}{2} = 1.

If both coordinates of the midpoint come out as whole numbers (like they do here), that’s a good sign your arithmetic is clean. NCERT problems are designed with integer answers — a decimal result mid-calculation usually signals a sign error.

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