Question 84 (i)
Simplify
(3x+2y)2+(3x−2y)2
We have (3x+2y)2+(3x−2y)2=(3x)2+(2y)2+2×3x×2y+(3x)2+(2y)2−2×3x×2y [using the identities, (a+b)2=a2+b2+2ab and (a−b)2=a2+b2−2ab] =9x2+4y2+12xy+9x2+4y2−12xy=(9x2+9x2)+(4y2+4y2)+12xy−12xy=18x2+8y2
Question 84 (ii)
(3x+2y)2−(3x−2y)2