Question

If 9a^2 + 16b^2 + c^2 + 25 = 24 (a + b) then find 3a+4b+5c.

Answer 1

Answer:

Expand: (3a + 4b + 5c)2.

Answer

We have,

(3a + 4b + 5c)2

We know that,

(a + b + c)2 = a2 + y2 + c2 + 2 (xy + yz + zx)

∴ (3a + 4b + 5c)2 = (9a2 + 16b2 + 25c2 + 2 × 3a × 4b + 2 × 4b × 5c + 2 × 5c × 3a)

= 9a2 + 16b2 + 25c2 + 24ab + 40bc + 30ac