Question

A certain shade of green paint is made from six
parts yellow mixed with four parts blue. If
seventy cans of paint was used in all, how many
cans of blue were used?

Explan me
Ans: 28​

Answer 1

3x – 7y = 10, xy = -1

3x -7y= 10

Squaring both sides,

(3x – 7y)2 = (10)2

⇒ (3x)2 + (7y)2 – 2 x 3x x 7y = 100

⇒  9X2 + 49y2 – 42xy = 100

⇒  9x2 + 49y2 – 42(-l) = 100

⇒ 9x2 + 49y2 + 42 = 100

∴ 9x2 + 49y2 = 100 – 42 = 58