Question

if x + y = 25,x-y = 15 then 2 (x+ y )(x-y) = ​

Answer 1

Answer:

Hmm

25+52=1525+52=15

25−52=1025−52=10

15+10=2515+10=25

15−10=515−10=5

Let’s see how this compares to the equations with variables only

(x+y)+(x−y)⟹2x=25+5(x+y)+(x−y)⟹2x=25+5

→2x2=302→2x2=302

⟶x=15⟶x=15

(x+y)−(x−y)⟹2y=25−5(x+y)−(x−y)⟹2y=25−5

→2y2=202→2y2=202

⟶y=10⟶y=10

Confirmed: x=15,y=10x=15,y=10

Q.E.D.

Answer 2

$x + y = 25 \\ x - y = 15$

$2(x + y)(x - y) = 2(25)(15) \\ = 50 \times 15 \\ = 750$