Since is the square of x and 6x is twice the product between x and 3, the second square must be 3 squared, i.e. 9.
So, if we think of 15 as 9+6, we have
Which is the required vertex form. This form tells us imediately that the vertex is the point (3,6).
Since the leading coefficient is 1, the parabola is facing upwards (it's U shaped), so the vertex is a minimum.
<em>Question:</em>
<em>Sal is trying to determine which cell phone and service plan to buy for his mother. The first phone costs $100 and $55 per month for unlimited usage. The second phone costs $150 and $51 per month for unlimited usage. </em>
<em>The inequality that will determine the number of months, x, that are required for the second phone to be less expensive is . </em>
<em>The solution to the inequality is . </em>
<em>Sal’s mother would have to keep the second cell phone plan for at least months in order for it to be less expensive.</em>
Answer:
a.
b.
c. At least 13 months
Step-by-step explanation:
Given
First Phone;
<em>(monthly)</em>
Second Phone;
<em /><em> (monthly)</em>
<em></em>
Solving (a): The inequality
<em></em>
Represent the number of months with x
The first phone is expressed as:
The second phone is expressed as:
For the second to be less expensive that the first, the inequality is:
Solving (b): Inequality Solution
Collect Like Terms
Solve for x
Solving (c): Interpret the solution in (b)
implies 13, 14, 15....
Hence, She'll keep the second phone for a period of at least 13 months