Question

Solve the simultaneous equations. to. 3 significant figures.
3x^2 + y^2 = 20
2x + y =3​

Answer 1

check explanation

Explanation:

in eqn 2,

y = 3 - 2x

substitute for it in eqn 1

3x² + y² = 20

3x² + (3 - 2x)² = 20

3x² + 9 - 12x + 4x² = 20

Group like terms;

3x² + 4x² - 12x = 20 -9

7x² - 12x = 11

x(7x - 12) = 11

x = 11,

OR

7x - 12 = 11

7x = 11 + 12

7x = 23

x = 23/7

x = 3.286

To get y, substitute for x in eqn 2

WHEN x = 11,

y = 3 - 2(11)

y = 3 - 22

y = -19

WHEN x = 3.286

y = 3 - 2(3.386)

y = -3.772