the quadratic formula work all the time because it is suitable for every equation.
Answer:
D 7
Step-by-step explanation:
Total no. of bulb= 5
no. of defected bulb= 3
no. of not defected bulb=2
Total no. of bulb combination = 5C2
=5!/2!(5-2)!
= 5!/2!3!
= 5×4×3×2×1/2×1×3×2×1
=120/12
=10
( since a room can be lighted with one bulb also)
total no. of bulb combination when room shall not light = 3C2
3!/2!(3-2)!
= 3!/2! 1!
= 3×2×1/2×1×1
= 6/2
=3
Now,
Total no. of trial when room shall light
=10-3
=7
Hence, number of trial when the room shall be lighted is 7 which is option d
Answer:
Therefore the equation of the line through ( -7 , 5 ) and ( -5 , 9) is
Linear Relationship i.e 
Step-by-step explanation:
Given:
Let,
point A( x₁ , y₁) ≡ ( -7, 5 )
point B( x₂ , y₂) ≡ (-5, 9)
To Find:
Equation of Line AB =?
Solution:
Equation of a line passing through Two points A( x₁ , y₁) and B( x₂ , y₂)is given by the formula

Substituting the given values in a above equation we get

Therefore the equation of the line through ( -7 , 5 ) and ( -5 , 9 ) is
Linear Relationship i.e 
Answer:
c.11
Step-by-step explanation:
h + 9 < 20
-9 -9
--------------------
h<20-9
h<11