Question
Two numbers x and y are connected by the equation x+y=12 and y²= 3x+4 find the value of x and y
Answers
mathhelper
from x+y=12 , x = 12-y
sub this into y²= 3x+4
y^2 = 3(12-y) + 4
y^2 = 36 - 3y + 4
y^2 + 3y - 40 = 0
(y + 8)(y - 5) = 0
y = -8 or y = 5
if y = 5, then x = 7
if y = -8, then x = 20
sub this into y²= 3x+4
y^2 = 3(12-y) + 4
y^2 = 36 - 3y + 4
y^2 + 3y - 40 = 0
(y + 8)(y - 5) = 0
y = -8 or y = 5
if y = 5, then x = 7
if y = -8, then x = 20