Please help me with this homework

Mathematics

1 answer:

fenix001 [56]2 years ago

3 0

A dollar and 92 cents

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Find the greatest solution for x+y when x^2+y^2 = 7, x^3+y^3=10

damaskus [11]

Answer:

Step-by-step explanation:

set

$f(x,y)=x+y\\$

constrain:

$g(x,y)=x^2+y^2 = 7\\h(x,y)=x^3+y^3=10$

Partial derivatives:

$f_{x}=1\\f_{y} =1 \\g_{x}=2x \\g_{y}=2y\\h_{x}=3x^2 \\h_{y}=3y^2$

Lagrange multiplier:

$grad(f)=a*grad(g)+b*grad(h)\\$

$\left[\begin{array}{ccc}1\\1\end{array}\right]=a\left[\begin{array}{ccc}2x\\2y\end{array}\right]+b\left[\begin{array}{ccc}3x^2\\3y^2\end{array}\right]$

4 equations:

$1=2ax+3bx^2\\1=2ay+3by^2\\x^2+y^2=7\\x^3+y^3=10$

By solving:

$a=4/9\\b=-2/27\\x+y=4$

Second mathod:

Solve for x^2+y^2 = 7, x^3+y^3=10 first:

$x=\frac{1}{2} -\frac{\sqrt{13}}{2} \ or \ y=\frac{1}{2} +\frac{\sqrt{13}}{2} \\x=\frac{1}{2} +\frac{\sqrt{13}}{2} \ or \ y=\frac{1}{2} -\frac{\sqrt{13}}{2} \\x+y=-5\ or\ 1 \or\ 4$

The maximum is 4

6 0

3 years ago

0.04 with 4 repeating as a fraction. Not the 04 repeating just the 4 is repeating. What is the answer???

Dmitriy789 [7]

Answer:

2/45

Step-by-step explanation:

0.04... is the same as 0.1 * 0.4... because we are moving it up a decimal place, it's the same as multiplying by ten: we needed to multiply by a tenth to cancel that out. 0.4... is the same as 4/9 and 0.1 is the same as 1/10. We can rewrite the expression above as: $(\frac{1}{10} )(\frac{4}{9} )$ . Multiplying the two fractions results in 4/90 which can be simplified to 2/45.