Question

find the value of 125x³+ 8y³ if 5x+2y=-7 and xy=2​

Answer 1

Answer:

\begin{gathered} {(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\end{gathered}

(5x−2y)

2

=6

2

25x

2

+4y

2

−20xy=36

25x

2

+4y

2

−20×4=36

25x

2

+4y

2

=36+80=116

\begin{gathered} {125x}^{ 3} - {8y}^{3} = \\ (5x - 2y)( {25x}^{2} + {4y}^{2} + 10xy)\end{gathered}

125x

3

−8y

3

=

(5x−2y)(25x

2

+4y

2

+10xy)

6×(116+10×4)

6×156=936

Answer 2

Answer: begin{gathered} {(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\end{gathered}

(5x−2y) 2

=6 2 25x 2+4y2 −20xy

=3625x2 +4y2 −20×4=36 25x 2 +4y 2

=36+80=116

begin{gathered} {125x}^{ 3} - {8y}^{3} = \\ (5x - 2y)( {25x}^{2} + {4y}^{2} + 10xy)\end{gathered}

125x 3 −8y 3

= (5x−2y)(25x 2 +4y 2 +10xy) 6×(116+10×4) 6×156=936

Step-by-step explanation: