If (3p - 5m) = 5 and pm = 6, then what is the value of $(9p^2 - 25m^2)$ ?
Answer & explanation
Correct answer: option 1
Given =
(3p - 5m) = 5
pm = 6
We know that,
(a - b)2 = a2 + b2 - 2ab
(a2 - b2) = (a - b)(a + b)
(a + b)2 = (a - b)2 + 4ab
Calculation:
= (3p + 5m)2 = (3p - 5m)2 + 4 × 3p × 5m
= 25 + 60 × 6
= (3p + 5m) = ±\(\sqrt {385}\)