Question

Evaluate

3x2−2xy+4y2
3
x
2
−
2
x
y
+
4
y
2
for
x=−1
x
=
−
1
and
y=−2

Answer 1

3x² -2xy + 4y² at x = -1, y = -2 = 15

Explanation:

Given function is

f(x, y) = 3x² -2xy + 4y²

To find At x = - 1 and y - 2 just plug these values for x and y into f(x, y)

f(-1, -2) = 3(-1)² - 2(-1)(-2) + 4(-2)²

(-1)² = 1 ==> 3x² = 3(-1)² = 3 x 1 = 3

(-1) (-2) = 2 ==> 2xy = 2(-1)(-2) = 2 x 2 = 4

(-2)² = 4 ==> 4y² = 4 (-2)² = 4 x 4 = 16

f(-1 1, - 2) = 3x² -2xy + 4y²
= 3 - 4 + 16

= 15