What is the value of the expression 2x^2 + 3xy - 4y^2 when x = 2 and y = -4?

Mathematics

1 answer:

Vera_Pavlovna [14]3 years ago

5 0

Answer:

-80

Step-by-step explanation:

2x^2 + 3xy - 4y^2

x = 2 | y = - 4

2(2)^2 + 3(2)(-4) - 4(-4)^2

2 * 4 + 3(2)(-4) - 4 * 16

8 - 24 - 64

-80

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Solve the system of equations by graphing. Check your solution. 5x+y=14 2x-y=7

Fudgin [204]

ANSWER

(3,-1)

EXPLANATION

The given system of equations is :

5x+y=14

2x-y=7

For the first equation when x=0,

5(0)+y=14

y=14

The y-intercept is (0,14).

When y=0, 5x+0=14

$x = \frac{14}{5} = 2 .8$

The x-intercept is (2.8,0).

We plot the intercepts and draw a straight line through them to obtain the graph of 5x+y=14 as shown in the attachment.

We repeat the same process for the second equation 2x-y=7.

The intercepts are (0,-7) and (3.5,0)

The solution to the system is the point of intersection of the two straight lines.

The two straight lines intersected at

(3,-1)

Hence x=2, y=-1