45x+25(10-x)≤400,400+50x+30(10-x)≥800的解

45x+25(10-x)≤400,400+50x+30(10-x)≥800的解 400(20-X)(10-X)+200×【20x+(10-X)X】=55000怎么算! 400x+10%(3000/x-400x)=2100 (x-21)(350-10x)=400 400=x^2+(x+x)^2 25％x+x=10 x=? [20%(600-x)+10%x]/600=10%(400-x)+20%x/400 （20-2x)(20-2x)x>400 x=? x/x^2-25-5/x^2+10x+25 x+50%x=400 (x^+x)^2-10(x^2+x)+25 x^2-10x+25 25=x(10-x), {x+x*10%≤150 {x+x*20%≥150{x+x*10%≤150{x+x*20%≥150 若-3≤x ≤2,化简|x-2|+根号（x+3）²+根号x²-10x+25 25x X 5 +15x X 10 +12x X 15 =7280 (40-x)(20+2x)=1200 800+80X-20X-2x^2=1200 -2x^2+60X-400=0 x^2-30X+200=0 (X-10)(X-20)=0 X-10=0 X-20=0(X-10)(X-20)=0 40-x)(20+2x)=1200 800+80X-20X-2x^2=1200 -2x^2+60X-400=0 ^2-30X+200=0 (X-10)(X-20)=0 解方程 6%x+19x=22.5 78%x - 117=39 400 - 50%x=180 50%x+2x=10有4题呀