Zrób odejmowanie

1. [tex]\frac{10x+3}{6x^2} - \frac{15-7x}{9x^3} =[/tex]

2. [tex]\frac{6}{b} - \frac{42}{b^2+7b} =[/tex]

3. [tex]\frac{c}{c+4} - \frac{c^2}{c^2-16} =[/tex]

4. [tex]\text 3y - \frac{18y^2}{6y+1} =[/tex]