1/2:1/5=1/4：x 0.8:4=x:8 2/9=8/ x
3/4:x=3:12 36/x=54/3 1.25:0.25=x:1.6
[试题]解下列方程（1）x/4-1/2=3/4（2）(7x-5)=3/8（3）(2x-1)/6=(5x+1)/8（4）(x/2)-7=(9x-2)/6（5）x/5-(3-2x)/2=1（6）(2x+1)/3-(5x-1)/6=1（7）(2x+14)=4-2x（8）3(200+x)-2(300-x)=300×(9/25)
) 3(x)_(1)+4(x)_(2)leqslant 9 5(x)_(1)+2(x)_(2)leqslant 8 (x)_(1),(x)_(2)geqslan
[试题]解下列方程：（1）5x/12-x/4=1/3（2）2/3-8x=3-x/2（3）0.5x-0.7=6.5-1.3x（4）(3x-6)/6=2x/5-3（5）3(x-7)+5(x-4)=15（6）4x-3(20-x)=-4（7）(y-1)/2=2-[(y+2)/5]（8）(1-2x)/3=2(3x+1)/7
) 3(x)_(1)+4(x)_(2)leqslant 9, 5(x)_(1)+2(x)_(2)leqslant 8, (x)_(1),(x)_(2)geqsl
用消元法解下列线性方程组:-|||- x1+3x2+5x3-4x4 =1, x1+3x2+2x3-2x4+x5=-1, x1-2x2+x3-x4-x5=3, x
t-|||- ) 3(x)_(1)+4(x)_(2)leqslant 9 5(x)_(1)+2(x)_(2)leqslant 8 (x)_(1),(x)_(2
解下列方程：(1)196x^2-1=0；(2)4x^2+12x+9=81；(3)x^2-7x-1=0；(4)2x^2+3x=3；(5)x^2-2x+1=25；(
求解下列齐次线性方程组-|||- ) (x)_(1)+2(x)_(2)-(x)_(3)+(x)_(4)=1 2(x)_(1)+4(x)_(2)-2(x)_(3
用公式法解下列方程．（1）x2+x-12=0（2）x2-sqrt(2)x-(1)/(4)=0（3）x2+4x+8=2x+11（4）x（x-4）=2-8x（5）x
求下列函数的导数： (1) =((2x+5))^4; (1) =((2x+5))^4; (1) =((2x+5))^4; (1) =((2x+5))^4; (1