Question

Зная,что 4,2<x<4,5,оцените:

3x-8; 6-х ; $frac{1}{x}$+1;$x^{2}+1,2$

Answer 1

$4,2<x<4,5\\\1);; 3x-8\\4,2<x<4,5 ;;big|times3\\12,6 -8< 3x - 8< 13,5-8 \\4,6 < 3x - 8 < 5,5$

$2);;6-x\\4,2<x<4,5 ;;big|times (-1)\\-4,5 +6< -x + 6< -4,2+6 \\1,5 < 6-x<1,8$

$3);; dfrac{1}{x}+1\\frac{1}{4,5} < frac{1}{x} < frac{1}{4,2} ;;;;;;;4,5 =frac{9}{2} ;;;;;4,2 = frac{21}{5}\\frac{2}{9} +1< frac{1}{x} + 1< frac{5}{21} +1\\1frac{2}{9} < frac{1}{x} + 1 < 1frac{5}{21}$

$4);;x^2 + 1,2\\4,2 times 4,2<xtimes x<4,5 times 4,5 \\17,64 +1,2< x^2 +1,2< 20,25+1,2\\18,84 < x^2+1,2 < 21,45$