Question

Jesli x+y=12 i x^2 +y^2=126, to x*y ma wartość:
a)9
b)10
c)11
d)13

prosze o obliczenia

Answer 1

A

jesli x+y=12 i x^2 +y^2=126, to x*y ma wartość:

(x+y)²=12²=144
(x+y)²=x²+2xy+y²=126+2xy
144=126+2xy
18=2xy
xy=9

Answer 2

X+y=12
x=12-y

x^2+y^2=126
(12-y)^2+y^2=126
144-24y+y^2+y^2=126
-24y+2y^2=126-144
-2y(12+y)=-18//-2
y(12+y)=9

dalej nie mogę

Answer 3

Jesli x + y = 12
i x² + y² = 126

(x + y)² = x² + 2xy + y²
(x + y)² = x² + y² + 2xy
12² = 126 + 2xy
2xy = 144 - 126
2xy = 18 |:2
xy = 9

odp a