1.

Find the value of 125x³ - 8y³ . If 5x - 2y = 6 and xy = 4 . Explain it in detail .

Answer»
{(5x - 2y)}^{2}  =  {6}^{2}   \\  {25x}^{2}  +  {4y}^{2}  - 20xy = 36 \\ {25x}^{2}  +  {4y}^{2} - 20 \times 4 = 36 \\ {25x}^{2}  +  {4y}^{2} = 36 + 80 = 116
{125x}^{ 3}  -  {8y}^{3}  =  \\ (5x - 2y)( {25x}^{2} +  {4y}^{2}   + 10xy)
6×(116+10×4)
6×156=936


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