Question

1)Calcule:
a) (+1/3 xy) - (-xy) +(-2 xy)
b) (-3 ab) - (+2 ab) - (-3 ab)
c) (-2/3 cd) . (9/12 c²d)
d) (-4/7 gh³) : (-21/8 g²h)

Answer 1

$a) ( +\frac{1}{3} xy)-(-xy)+(-2xy)= \\ \\ = \frac{xy}{3} +xy-2xy= \\ \\ =\frac{xy+3xy-6xy}{3} = \\ \\ =\frac{4xy-6xy}{3} = \\ \\ = \frac{-2xy}{3} \\ \\ \\ b)(-3ab)-(+2ab)-(-3ab)= \\ \\ =-3ab-2ab+3ab= \\ \\ -5ab+3ab= \\ \\ -2ab$

$c)(- \frac{2}{3} cd).( \frac{9}{12} c^2d)= \\ \\ =- \frac{2cd}{3} . \frac{9c^2d}{12} =- \frac{c^3d^2}{2} \\ \\ d)(- \frac{4}{7} gh^3):(- \frac{21}{8} g^2h)= \\ \\ = \frac{-4gh^3}{7} : \frac{-21g^2h}{8} = \\ \\ =\frac{-4gh^3}{7}. \frac{8}{-21g^2h} = \\ \\ = \frac{32h^2}{147g}$