Question

Решить 4,5,6,7. С описанием срочно

Answer 1

$4)\; \; a)\; \left \{ {{-2x\geq 8} \atop {5x-1<9}} \right.\; \left \{ {{x\leq -4} \atop {x<2}} \right. \; \; \to \; \; x\leq -4\; \; ;\; \; \underline {-8\in (-\infty ,-4\, ]\; }\\\\\left \{ {{-5x\leq -10} \atop {3x+2>5}} \right.\; \left \{ {{x\geq 2} \atop {x>1}} \right. \; \; \to \; \; x\geq 2\; \; ;\; \; \underline {5\in [\, 2,+\infty )\; }\\\\\\5)\; \; \left \{ {{x+1<9} \atop {-2x<6}} \right.\; \left \{ {{x<8} \atop {x>-3}} \right. \; \; \to \; \; x\in (-3,8)\\\\\left \{ {{x-2>8} \atop {-3x<9}} \right.\; \left \{ {{x>10} \atop {x>-3}} \right. \; \; \to \; \; x>10\; \; ;\; \; x\in (10,+\infty )$

$6)\; \; ybuvaet:\; \; x\in (-\infty ,1\, ]\\\\vozrastaet:\; \; x\in [\, 1,+\infty )\\\\7)\; \; 6<x<8\; \; ,\; \; 8<y<10\\\\-40<-5x<-30\qquad \qquad \; \; \; \qquad  -30<-5y<-40\\\\8-40<y-5x<10-30\qquad \qquad 6-30<x-5y<8-40\\\\-32<y-5x<-20\qquad \qquad \qquad \qquad -24<x-5y<-32$