Q. The solution of the equation $(x + 1) + (x + 4) + (x + 7) + ... + (x + 28) = 155$ is
A) 1
B) 2
C) 3
D) 4
Explanation
(a)
$\because(x + 1) + (x + 4) + (x + 7) + ... + (x + 28) = 155$
Let $n$ be the number of terms in the AP on LHS.
$\therefore\ x + 28 = (x + 1) + (n - 1)3$
$\Rightarrow n = 10$
$\therefore\ \frac{10}{2}\left\lbrack (x + 1) + (x + 28) \right\rbrack = 155$
$\Rightarrow \ x = 1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.