4.
[tex]5(y^{2}-8)-(18-8y^{2}) = 5y^{2}-40-18+8y^{2}=13y^{2}-58[/tex]
Wyjaśnienie:
Jeżeli przed nawiasem jest znak minus (-), to po uwolnieniu od nawiasu zmieniamy znaki na przeciwne.
5.
[tex]a) \ \frac{x}{3}=\frac{7}{6}\\\\6x = 21 \ \ /:6\\\\x = \frac{21}{6}\\\\\boxed{x = 3\frac{3}{6} = 3\frac{1}{2}}[/tex]
[tex]b) \ \frac{x+2}{4} = \frac{x}{5}\\\\5(x+2) = 4x\\\\5x+10 = 4x\\\\5x-4x = -10\\\\\boxed{x = -10}[/tex]
6.
[tex]a) \ 3x-5 = 7 +x\\\\3x-x = 7+5\\\\2x = 12 \ \ /:2\\\\\boxed{x = 6}[/tex]
[tex]b) \ 2(x+3)+4 = 1-x\\\\2x+6+4 = 1-x\\\\2x+10 = 1-x\\\\2x+x = 1-10\\\\3x = -9 \ \ /:3\\\\\boxed{x = -3}[/tex]
