Zadanie 1.
We wszystkich przykładach zastosuję mnożenie "na krzyż".
a) [tex]\frac{x}{3}[/tex] = [tex]\frac{-4}{5}[/tex], czyli
x * 5 = -4 * 3
5x = -12 /:(5)
x = - [tex]\frac{12}{5}[/tex]
x = - 2[tex]\frac{2}{5}[/tex]
b) [tex]\frac{2}{2y-1}[/tex] = [tex]\frac{4}{5}[/tex]
2 *5 = 4 * (2y-1)
10 = 8y - 4
10 + 4 = 8y
8y = 14 /:(8)
y = [tex]\frac{14}{8}[/tex]
y = 1[tex]\frac{3}{4}[/tex]
c) [tex]\frac{4}{z-1}[/tex] = [tex]\frac{5}{z+2}[/tex]
4 * (z+2) = 5 * (z-1)
4z + 8 = 5z - 5
8 + 5 = 5z - 4z
z = 13
