Evaluate formulas with "+" symbols For problems that involve using a "+" we must realize there will be two answers; this symbol is asking us to both subtract and add the quantity after the symbol to the value(s) before the symbol. When given the formula x I I zs we are really being given the two equations x I T 7zs and tering x 0 2 I zs . Note we usually write the one with the "-"first, as mathematically that will be the smaller of the two values. Since this type of equation usually yields an interval, the smaller number should come first. Example 1: Given: x X zs , find the two values of x if a [ 150.4, z / 1.645, s [ 18.2 x x zs, x la ks x 150.4 1.645(18.2), x [ 150.4 0 1.645(18.2) x 150.4 29.939, x [ 150.4 29.939 x 120.461, x 180.339 x 120.46, x 180.34 Since there are two values that are called x, depending on the context of the problem we can give them subscripts such as x, [ 120.46, x, [ 180.34 or we can write them mas the interval: (120.46, 180.34) . Note that the smaller of the two values is always written first in the answer. Find the two values of x for x [ a I ts , if a 55.32, + 1 2.065, s 1 7.82 When x I I ts Use x [ / ts, x 1 &0] is The two values are (