x+(28+x)*3/4=42

x+(28+x)*3/4=42 3/4（x+28)=42-x x+(28+x)*3/4=42 x+5/x+1-3x-3/x+5=8x+28/x^2+4X-5-2（x+5）/（x+1)-(3x-3)/(x+5)=(8x+28)/(x^2+4X-5)-2 (求解、x+5)/(x-1)-(3x-3)/(x+5)=(8x+28)/(x^2+4x-5)-2 一个“整式的乘法”的问题请先阅读下列解题过程,再仿做下面的问题.已知X*X + X - 1=0,求X*X*X + 2*X*X + 3的值.解X*X*X + 2X*X +3=X*X*X +X*X -X +X*X +X +3=X{X*X +X -1} +X*X +X -1 +4=0+0+4=4+ x + X*X + X*X*X=0.+ X*X + X*X*X x+2x+3x+4x+5x+6x+7x+8x+9x=9x-8x-7x-6x-5x-4x-3x-2x-x.x等于多少? x(x^2-1)+2x^2 *(x+1）-3x*(2x-5)=x(3x^2-4x)-28 解分式方程：1/X-2+1/X-6=1/X-7+1/X-11/X-2+1/X-6=1/X-7+1/X-11/(x-2)-1/(x-1)=1/(x-7)-1/(x-6)(x-1-x+2)/(x-2)(x-1)=(x-6-x+7)/(x-7)(x-6)1/(x-2)(x-1)=1/(x-7)(x-6)(x-2)(x-1)=(x-7)(x-6)x^2-3x+2=x^2-13x+4213x-3x=42-210x=40x=4 为什么要移向才能解 (1) 3x-42=9x-2 (2) 2x-5(3-2x)=10 (3) 2(2x+1)-(5x-1)=6 (4)2x+14=28-14x(5）2（x-2）-3（4x-1)=9(1+x)(6)11x+64+2x=100-9x(7）15-（8-5x）=7x+（4-3x）（8）30x-10(10-x）=100 (x-3/x-2)-(x-2/x-1)=(x-5/x4) -(x-4/x-3) x-2x+3x-4x+5x.+99x-100x=25求解 2x+3x+4x+5x+x+6x+7x=100 x(x+1)+(x+2)+(x+3)+(x+4)+(x+5) = 27求x 下列式子求导1.f(x)=x^3-3x^2+3x-22.g(x)=-3x^3+5x^2-4x+113.u(x)=-x^3+27x+74.h(x)=42-45x-3x^2+3x^35.f(x)=Lnx+x6.g(x)=x/(2+x^2) x-4/1x=8/3 x-0.8x=22 3/2x+2/1x=42x-4/1x=8/3 x-0.8x=22 3/2x+2/1x=42 x+(28+x)*3=42 X+X+X+(X-1)+(X-2)+(X-3)+(X-4)=10(X-3)+(X-4)