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There are $25$ points on a plane of which $7$ are collinear . How many quadrilaterals can be formed from these points ?
I did this $^{25}C_{4}-^{7}C_{4}=12615$ quadrilaterals.
But the book is giving answer $^{25}C_{4}-^{7}C_{4}-^{7}C_{3}\times ^{18}C_{1}=11985$ quadrilaterals..
I don't know what is the correct idea .
I look for a short and simple way.
I have studied maths up to $12$th grade.
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