690
12×36 + 258 = 690 For extending to 20 characters
2x-1 < x+3
5x-1 > 6-2x
x-5 < 0
solve the inequality for x.
x < 4
x > 1
X < 5
find the intersection
X ∑ {1,4}
Alternative form: {x I 1 < x < 4}
∑ indicates summation and is used as a shorthand notation for the sum of terms that follow a pattern. For example, the sum of the first 4 squared integers, 12+22+32+42, follows a simple pattern: each term is of the form i2, and we add up values from i=1 to i=4.
