Решите 1. (2/3)^x>1 1/2 2. 9^2x≤1/3 3. (1/7)^x^2-9≤1 4. 4^x+2^x+1-80<0 5. (1/3)^t<1/27

Лебедев Дмитрий Сергеевич

Учитель математики

Проверено учителем

Решениями неравенств являются: 1) x<-1x is less than negative 1; 2) x-0,25x is less than or equal to negative 0 comma 25; 3) x(;-3][3;+)x is an element of open paren negative infinity ; negative 3 close bracket union open bracket 3 ; positive infinity close paren; 4) x<3x is less than 3; 5) t>3t is greater than 3. Шаг 1: Решение неравенства (2/3)x>112open paren 2 / 3 close paren to the x-th power is greater than 1 and one-half Представим правую часть в виде степени с основанием 2/32 / 3: 112=32=(23)-11 and one-half equals three-halves equals open paren two-thirds close paren to the negative 1 power Исходное неравенство: (2/3)x>(2/3)-1open paren 2 / 3 close paren to the x-th power is greater than open paren 2 / 3 close paren to the negative 1 power Так как основание степени 0<2/3<10 is less than 2 / 3 is less than 1, при переходе к показателям знак неравенства меняется на противоположный: x<-1x is less than negative 1 Шаг 2: Решение неравенства 92x1/39 raised to the 2 x power is less than or equal to 1 / 3 Приведем обе части к основанию 33: (32)2x3-134x3-1open paren 3 squared close paren raised to the 2 x power is less than or equal to 3 to the negative 1 power implies 3 raised to the 4 x power is less than or equal to 3 to the negative 1 power Так как основание 3>13 is greater than 1, знак неравенства сохраняется: 4x-1x-1/4x-0,254 x is less than or equal to negative 1 implies x is less than or equal to negative 1 / 4 implies x is less than or equal to negative 0 comma 25 Шаг 3: Решение неравенства (1/7)x291open paren 1 / 7 close paren raised to the exponent x squared minus 9 end-exponent is less than or equal to 1 Представим единицу как (1/7)0open paren 1 / 7 close paren to the 0 power: (1/7)x29(1/7)0open paren 1 / 7 close paren raised to the exponent x squared minus 9 end-exponent is less than or equal to open paren 1 / 7 close paren to the 0 power Основание 1/7<11 / 7 is less than 1, следовательно, меняем знак: x290(x3)(x+3)0x squared minus 9 is greater than or equal to 0 implies open paren x minus 3 close paren open paren x plus 3 close paren is greater than or equal to 0 Решая методом интервалов, получаем: x(;-3][3;+)x is an element of open paren negative infinity ; negative 3 close bracket union open bracket 3 ; positive infinity close paren Шаг 4: Решение неравенства 4x+2x+180<04 to the x-th power plus 2 raised to the x plus 1 power minus 80 is less than 0 Преобразуем выражение: (2x)2+22x80<0open paren 2 to the x-th power close paren squared plus 2 center dot 2 to the x-th power minus 80 is less than 0. Введем замену y=2xy equals 2 to the x-th power, где y>0y is greater than 0: y2+2y80<0y squared plus 2 y minus 80 is less than 0 Найдем корни уравнения y2+2y80=0y squared plus 2 y minus 80 equals 0: D=44(-80)=324=182cap D equals 4 minus 4 open paren negative 80 close paren equals 324 equals 18 squared. y1=-2+182=8y sub 1 equals the fraction with numerator negative 2 plus 18 and denominator 2 end-fraction equals 8 , y2=-2182=-10y sub 2 equals the fraction with numerator negative 2 minus 18 and denominator 2 end-fraction equals negative 10 . Решение квадратного неравенства: -10<y<8negative 10 is less than y is less than 8. Учитывая y>0y is greater than 0, получаем 0<y<80 is less than y is less than 8: 2x<23x<32 to the x-th power is less than 2 cubed implies x is less than 3 Шаг 5: Решение неравенства (1/3)t<1/27open paren 1 / 3 close paren to the t-th power is less than 1 / 27 Представим правую часть как степень с основанием 1/31 / 3: (1/3)t<(1/3)3open paren 1 / 3 close paren to the t-th power is less than open paren 1 / 3 close paren cubed Так как основание 1/3<11 / 3 is less than 1, знак неравенства меняется: t>3t is greater than 3 Ответ:

  1. x<-1x is less than negative 1
  2. x-0,25x is less than or equal to negative 0 comma 25
  3. x(;-3][3;+)x is an element of open paren negative infinity ; negative 3 close bracket union open bracket 3 ; positive infinity close paren
  4. x<3x is less than 3
  5. t>3t is greater than 3

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