Question

geometric isomerism explain it please it is important

Answer 1

It's very easy to miss geometric isomers in exams if you take short-cuts in drawing the structural formulae. For example, it is very tempting to draw but-2-ene as

CH3CH=CHCH3

If you write it like this, you will almost certainly miss the fact that there are geometric isomers. If there is even the slightest hint in a question that isomers might be involved, always draw compounds containing carbon-carbon double bonds showing the correct bond angles (120°) around the carbon atoms at the ends of the bond. 

Answer 2

Geometrical usomerism means isomers with same structureal formula but differ in Spital arrangement of group around the double bond called geometrical isomarisam and they are called cis:trans isomarisam and they present in opposite side of double bond then Trans;isomers.
Ex 2-buten