All together, Dion and trevor worked a total of 38 hours last week. If Dion worked d hours, which expression represent the numbe
1 answer:
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9514 1404 393
Answer:
y = 3.02x^3 -5.36x^2 +5.68x +8.66
Step-by-step explanation:
Your graphing calculator (or other regression tool) can solve this about as quickly as you can enter the numbers. If you have a number of regression formulas to work out, it is a good idea to become familiar with at least one tool for doing so.
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If you're trying to do this by hand, the x- and y-values give you 4 equations in the 4 unknown coefficients.
a·1^3 +b·1^2 +c·1 +d = 12
a·3^3 +b·3^2 +c·3 +d = 59
a·6^3 +b·6^2 +c·6 +d = 502
a·8^3 +b·8^2 +c·8 +d = 1257
Solving this by elimination, substitution, or matrix methods is tedious, but not impossible. Calculators and web sites can help. The solutions are a = 317/105, b = -75/14, c = 1193/210, d = 303/35. Approximations to these values are shown above.
Answer:
2
Step-by-step explanation:
So I'm going to use vieta's formula.
Let u and v the zeros of the given quadratic in ax^2+bx+c form.
By vieta's formula:
1) u+v=-b/a
2) uv=c/a
We are also given not by the formula but by this problem:
3) u+v=uv
If we plug 1) and 2) into 3) we get:
-b/a=c/a
Multiply both sides by a:
-b=c
Here we have:
a=3
b=-(3k-2)
c=-(k-6)
So we are solving
-b=c for k:
3k-2=-(k-6)
Distribute:
3k-2=-k+6
Add k on both sides:
4k-2=6
Add 2 on both side:
4k=8
Divide both sides by 4:
k=2
Let's check:
:
I'm going to solve for x using the quadratic formula:
Let's see if uv=u+v holds.
Keep in mind you are multiplying conjugates:
Let's see what u+v is now:
We have confirmed uv=u+v for k=2.