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2 years ago

Use substitution to solve the system of equations :

Mathematics

1 answer:

mote1985 [20]2 years ago

3 0

Answer:

x=1

y=-4

Step-by-step explanation:

4x+y=0 -> y= -4x

2(-4x)+x=-7

-8x+ x=-7

-7x=-7

x=-7/-7=1

y=-4 . 1 = -4

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How to solve this question

VMariaS [17]

<span>The variance method is as follows.

-Sum the squares of the values in data set, and then divide by the number of values in data set
- From that, subtract the square of the mean (add all values and divide by number of values in the data set)

Our variance is

<span> $\displaystyle\sigma^2 = \frac{2^2 + 5^2 + m^2}{3} - \left(\frac{2 + 5 + m}{3}\right)^2$

Since variance has to be 14, we set $\sigma^2 = 14$ and solve for m

$14= \frac{4 + 25 + m^2}{3} - \left(\frac{7 + m}{3}\right)^2\ \Rightarrow \\ \\
14 = \frac{29}{3} + \frac{1}{3}m^2 - \frac{1}{9}(7+m)^2 \\ \\
14 = \frac{29}{3}+ \frac{1}{3}m^2 - \frac{1}{9}(49 + 14m + m^2) \\ \\
14 = \frac{29}{3}+ \frac{1}{3}m^2 - \frac{49}{9}- \frac{14}{9}m- \frac{1}{9}m^2 \\ \\
0 = \frac{-88}{9} -\frac{14}{9}m + \frac{2}{9}m^2
$

quadratic formula

$m = \displaystyle\frac{-b \pm \sqrt{b^2 -4ac}}{2a} \\
m = \frac{-(-\frac{14}{9}) \pm \sqrt{\left(-\frac{14}{9}\right)^2 - 4(2/9)(-88/9)} }{2(2/9)} \\
m = \frac{\frac{14}{9} \pm \sqrt{ \frac{196}{81} + \frac{704}{81} } }{\frac{4}{9} } \\
m = \frac{\frac{14}{9} \pm \sqrt{ \frac{900}{81} } }{\frac{4}{9} } \\
m = \frac{\frac{14}{9} \pm \sqrt{ \frac{100}{9} } }{\frac{4}{9} } \\
m = \frac{\frac{14}{9} \pm \frac{10}{3} }{\frac{4}{9} } \\
m = 11, -4$

-4 doesnt' work as it is not a positive integer

m = 11

</span></span>

5 0

2 years ago

Twice as number decreased by 9 is 7

marissa [1.9K]

You said that. 2x - 9 = 7 . . . . . Add. 9. to each side: 2x = 16 . . . . . Divide each side by 2 : x = 8

8 0

3 years ago

H=4(x+3y)+2 make x the subject

blagie [28]

H = 4(x + 3y) + 2
H = 4x + 12y + 2
H - 12y - 2 = 4x
(H - 12y - 2) / 4 = x or 1/4H - 3y - 1/2 = x

5 0

2 years ago

Read 2 more answers

osiah invests $360 into an account that accrues 3% interest annually. Assuming no deposits or withdrawals are made, which equati

sammy [17]

The standard compound interest formula is

Future value after x years with an annual interest of i

=Present Value (1+i)^x [which is an exponential function]

for given present value of $360. interest=0.03 (3%) and a total of x years, above equation reduces to

Future value after x years

=360(1.03^x)

4 0

3 years ago

If A = 3x power 2+2y + 2 and B=6x power 2 - 8y + 1 then A+B and A-B

ollegr [7]

Answer:

see explanation

Step-by-step explanation:

Given A = 3x² + 2y + 2 and B = 6x² - 8y + 1 , then

A + B

= 3x² + 2y + 2 + 6x² - 8y + 1 ← collect like terms

= 9x² - 6y + 3

-------------------------------

A - B

= 3x² + 2y + 2 - (6x² - 8y + 1) ← distribute parenthesis by - 1

= 3x² + 2y + 2 - 6x² + 8y - 1 ← collect like terms

= - 3x² + 10y + 1

5 0

2 years ago