Answer:

Step-by-step explanation:
Given, f ( x ) = - x - 3
Let's find the value of f ( - 4 )

We know that , 
⇒
Subtract 3 from 4
⇒
Hope I helped!
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5x+2y=7
7x-2y=5 its subtract not add
Answer:
acute
Step-by-step explanation:
Here are some helpful rules that will help you out in the future with these questions.
If...
a^2 + b^2 = c^2 its a right triangle
a^2 + b^2 < c^2 its obtuse
a^2 + b^2 > c^2 its acute
so...
Since 6+8>10
its acute
X = low-energy lamp
y = high-energy lamp
1) 4x + 5y
2) 120= 4x + 5y