Q11. (1/1.4 + 1/4.7 + 1/ 7.10 + 1/10.13 + 1/13.16) = ?
= (1/3)[(1/1 – 1/4) + (1/4 – 1/7) + (1/7 – 1/10) + (1/10 – 1/13) + (1/13 – 1/16)
= (1/3)[(1/1 – 1/16)]
= (1/3)(15/16)
= 15/48
Q12. [x2 – (y – z)2]/[(x + z)2 – y2] + [y2 – (x – z)2]/[(x + y)2 – z2] + [z2 – (x – y)2]/[(y + z)2 – x2] = ?
[(x – y + z)(x + y – z)]/[(x + z – y)(x + z + y)] + ……………..
= [(x + y – z)/(x + z + y) + (x – y + z)/(x + z + y) + (-x + y + z)/(x + z + y)]
= (x + y + z)/(x + y + z)
= 1
