0.75-x=1 8

3x-18=13.23x=13.2+18x=10.41.5x-x=60.5x=6x=6/0.5=124x+1.2x=265.2x=26x=5

(1)0.25x=-5x=-20(2)3x-4x=1-5x=4(3)3x-4x=18-5x=-13(4)1+7=x+7xx=1(5)9x-7x-3x=-8x=8(6)-x+3x=3-2x=1/2(7)

原式:X^2-5X+6+18=X^2+10X+9-5X+24=10X+915X=15X=1

(X-X*20%-18)-（X-X*20%-18）*10%=X*1/2-3则（X*80%-18）*90%=X*1/2-372%*X-16.2=X*1/2-322%*X=13.2X=60

1/x（x+3)+1/（x+3)(x+6)+1/（x+6)(x+9）=3/2（x+9)（1/3）×[3/x（x+3)+3/（x+3)(x+6）+3/（x+6）（x+9)]=3/2（x+9）（1/3)[

（X+X)+(X-X)+(X*X)+(X/X)=1002X+0+X*X+1=1002X+X*X=99X(X+2)=99X=9再问：请问X(X+2)=99解为什么就等于9了呢没看懂再答：换成算术法你就明

解(1)x-0.75x=120.25x=121/4x=12x=12×4x=48(2)2.8x+x=7.63.8x=7.6x=7.6÷3.8x=2(3)2.36x+2.64x=185x=18x=18÷5

x(x-1)=18x-x=18x-x+1/4=18+1/4(x-1/2)=73/4x=1/2±√73/2

10（x+2)+x-18=10x+x+2x11x+2=13x2x=2x=1

x^4-4x^3-4x^2+15x+18=0x^4-3x^3-x^3+3x^2-7x^2+21x-6x+18=0(x-3)(x^3-x^2-7x-6)=0x1=3x2=3.49449283705542

0.3X=18X=60

设x1=4-√3,x2=4+√3,是方程X^2-8X+13=0的两根所以X1^2-8X1+15=2X^4-6X^3-2X^2+18X+23=(X+1)^2*(X^2-8X+13)+10=10所以原式=

1/[x(x+3)]+1/[(x+3)(x+6)]+.+1/[(x+15)(x+18)]=1/3[1/x-1/(x+3)]+[1/(x+3)-1/(x+6)]+.+[1/(x+15)-1/(x+18)

1/x(x+3)+1/(x+3)(x+6)+1/(x+6)(x+9)=[1/x-1/(x+3)+1/(x+3)-1/(x+6)+1(x+6)-1/(x+9)]/3=[1/x-1/(x+9)]/3=3/

方程是啥?如果为：x^0.75-x^0.25=0.75令t=x^0.25,则x^0.75=t^3方程化为:t^3-t=0.75,解得：t=1.26255112740716x=t^4=2.5409486

x/(x+3)-x/(3-x)=18/(x平方-9﹚x／﹙x+3﹚＋x／﹙x－3﹚＝18／﹙x+3﹚﹙x－3﹚x﹙x－3﹚＋x﹙x+3﹚＝182x²＝18x＝±3

3.5X—1.5X=10.82x=10.8x=5.42.36X+2.64X=185x=18x=3.6X—0.75x=120.25x=12x=482.8X+X=7.63.8x=7.6x=2

（5+1）X=186X=18X=3

10x-3.14*x*x*0.25=3.14*x*x*0.7510x=3.14*x*x*0.75+3.14*x*x*0.253.14*x*x*(0.75+0.25)-10x=03.14*x*x-10x

问题是不是X2=(X+30)*(X-18）啊?要是上面的话就这样X2=X*X-X*18+30*X-30*18=X2+12X-540移项得：X2-X2-12X=-540,即-12X=-540,X=45*