Question

If 3x +4y=16 and 3x-4y=4, find the value of xy.​

Answer 1

Answer:

Step-by-step explanation:

Answer 2

$3x + 4y = 16$

$squaring \: both \: side$

$(3x + 4y) {}^{2} = 256 - - - - (1)$

$also$

$3x - 4y = 4$

$squaring \: both \: side$

$3x - 4y {}^{2} = 16 - - - - - (12)$

Subtracting equation (1)from(2)

$(3x + 4y) {}^{2} - (3x - 4y) {}^{2} = 256 - 16$

$we \: know \: that \: (p + q) {}^{2} - (p - q) {}^{2} = 4pq$

4*3x*4y=240

4xxy=240

xy=240/48=5

so xy=5