0.3乘500=1500.3乘4000X=1200X-X乘500=-500X-X乘4000X=-4000X2(是X的平方)150+1200X-500X-4000X2(是X的平方)=180-4000X2(是X的平方)+700X=30-400X2(是X的平方)+70X-3=0400X2(是X的平方)-70X+3=040 -310 -1...