Answer:
Step-by-step explanation:
Given :
l + m + n = 9
l²+ m² + n²= 31
l + m + n = 9
On squaring both sides
(l + m + n)²= 9²
(l²+m²+n²+2(lm+mn+nl) = 81
31 +2(lm+mn+nl) = 81
2(lm+mn+nl) = 81 - 31
2(lm+mn+nl) = 50
(lm+mn+nl) = 50/2
(lm+mn+nl) = 25
Hence, the value of (lm+mn+nl) = 25
