I would personally add 6x to both sides to give 10x=-28, then divide by 10 to give x=-2.8
Collect the x's on one side
X²+10x+21=0
/\ = 10²-4*1*21
/\ = 100 - 84
/\ = 16
x = (-10+/-\/16)/2
x = (-10+/-4)/2
x' = (-10+4)/2 = -6/2 = -3
x" = (-10-4)/2 = -14/2 = -7
S: {-3; -7}
Answer:
-35
Step-by-step explanation:
- 4ac = (1)(1) - 4(-3)(3) = 1 - 36 = -35
Assume the old of Jack is X and the old of Lacy is Y
so ...
do the mathematical model ...
.
X=2Y
(X+7)+(Y+7)= 35
-
THEN
Solve the equation
y= 7
x = 14
