Question

If X+Y=7 and XY=2 then (X+Y)(X-Y)=?

Answer 1

Answer:

$7 \sqrt{41}$

Step-by-step explanation:

x+y=7

xy = 2

$(x + y) {}^{2} - 4xy = (x - y) {}^{2}$

so,

${7}^{2} - 4(2) = (x - y) {}^{2} \\ (x - y) {}^{2} = 41 \\ x - y = \sqrt{41}$

$(x + y)(x - y) = 7 \times \sqrt{41}$