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t in (-oo:+oo)
7*(4-(2*t)) = -42 // + 42
7*(4-(2*t))+42 = 0
7*(4-2*t)+42 = 0
7*(4-2*t)+42 = 0
70-14*t = 0
70-14*t = 0
70-14*t = 0 // - 70
-14*t = -70 // : -14
t = -70/(-14)
t = 5
t = 5
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