Pick any of the two sides and set them equal to one another. So we'll have three different equations
4(x-1) = x+8
or
x+8 = 2x+4
or
4(x-1) = 2x+4
This works because in any equilateral triangle, the three sides are the same length.
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If you're curious about the value of x, then we could do the following steps.
x+8 = 2x+4
2x+4 = x+8
2x-x = 8-4
x = 4
If x = 4, then
- 4(x-1) = 4(4-1) = 12
- x+8 = 4+8 = 12
- 2x+4 = 2*4+4 = 12
Each side is 12 units long
