Question

# Expand (3x−2y+4)(3x−2y−4)9x2−12xy+4y2−169x2+12xy+4y2+1627x2−12xy+4y2−927x2−12xy+4y2−16

Solution

## The correct option is A 9x2−12xy+4y2−16[(3x−2y)+4][(3x−2y)−4] Taking 3x - 2y = a = (a + 4)(a - 4) = a2−16         .......[ (a + 4)(a - 4) = a2−42] = (3x−2y)2−16 = (3x)2−2×3x×2y+(2y)2−16 = 9x2−12xy+4y2−16

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