Question

If a, b, c, d are in H.P., then ab + bc + cd = (a) ad (b) 2ad (c) 3ad (d) none of these

Answer 1

Step-by-step explanation:

Since a, b, c, d are in HP, c−1+a−1=2b−1 and d−1−b−1=c−1−a−1.

(c−1+a−1)(d−1−b−1)(cd)−1+(ad)−1−(ab)−1−(bc)−1(cd)−1+(ad)−1+(ab)−1(abcd)[(cd)−1+(ad)−1+(ab)−1]ab+bc+cd=2b−1(c−1−a−1)=2(bc)−1−2(ab)−1=3(bc)−1=(abcd)[3(bc)−1]=3ad

Answer 2

In the leaves, xylem and phloem together called vascular bundle. These are found in veins or veinlets. So, the correct option is 'Veins and Veinlets'.