Question

if x+2y=10 and xy=8 find the value od (1) x2+4y2 and (2) x-2y

Answer 1

if x+2y=10

=x=10-2y

and xy=8

(10-2y)y=8

=10y-2y×y=

Answer 2

Answer:

x+2y=10(Given)

For x=4

2y=10−4⇒y=3

For y=4

x=2

x4 2 y 34 

2x+4y=8(Given)

⇒x+2y=4

For x=2

2y=4−2⇒y=1

For y=3

x=−2

x2 −2 y 13 

Since the graph consists of a pair of parallel lines, the system of equations has no solution.

Also, the graph x+2y=10 cuts the x and y-axis at (10,0) and (0,5) respectively, while the graph of 2x+4y=8 cuts the x and y-axis at (4,0) and (0,2) respectively.