2.1X+3.9x=12

2.1X+3.9x=12 matlab中a=[x(11)/x,x(12)/x;x(21)/x,x(22)/x;x(31)/x,x(32)/x;x(41)/x,x(42)/x;x(51)/x,x(52)/x]咋错了 如果3x*x-x=1那么9x*x*x*x+12x*x*x-3x*x-7x+2001等于多少 5x+2x=33.6,7x-4x=0.75,2x+7x+2.1=12,56x-32x-119=361,解方程 (x+12)(x-2)+(x+7)(x+8)-(x+5)(x-10),其中x=2 3.6x*(2.1-x)=4.8x 4.2-0.6x=3.6x 5x+2x=33.6 7x-4x=0.75 2x+7x+2.1=12 56x-32x-119=361 x+5=2x 3x+9=6x 4x-28=2x 2x+18=7x 5x=25*4-15x 7x-x+2*3=29.4 (28.8+5.5x+3.2）除2=71 （X+X)+(X-X)+(X*X)+(X/X)=100 (1) 2.5+3X=1.1 (2) 12X-5X=2.1 (3) X-0.3X=1.4 X=1.1 X=2.1 X=1.4 X=?X=0.3 X=? x+(x-12)+(x-8)=70 60%X + 80%X - 12 = X x(x+4)=8x+12 x平方=(24-x)(12-x) x(x+4)=8x+12 14x=12+x 求X 2.4x-x=2.1 解方程：x-12=[x-(x-12)]/(x-12) (x+12)*(x+12)=x*x+360怎么解