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3 years ago

What is the solution to the system of equations 3x+2y=39 5x-y=13

Mathematics

1 answer:

Marta_Voda [28]3 years ago

8 0

3x + 2y = 39

5x - y = 13

Multiplying the last by two:

10x - 2y = 26

Adding to the first

13x = 65

x = 5

y = 5x-13 =25-13=12

Check:

3(5)+2(12)=39 good

5(5)-12=13 good

Answer: x=5, y=12

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<h3>Answer: True</h3>

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3 years ago

What two numbers multiply to -126 and add up to -65

Airida [17]

Xy = -126
x + y = -65

$xy = -126$
$\frac{xy}{x} = \frac{-126}{x}$
$y = \frac{-126}{x}$

$x + y = -65$
$x + \frac{-126}{x} = -65$
$\frac{x^{2}}{x} + \frac{-126}{x} = -65$
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$0 = x^{2} + 65x - 126$
$x = \frac{-(65) \+ \sqrt{(65)^{2} - 4(1)(-126)}}{2(1)}$
$x = \frac{-65 \± \sqrt{4225 + 504}}{2}$
$x = \frac{-65 \± \sqrt{4729}}{2}$
$x = \frac{-65 \± 68.8}{2}$
$x = \frac{-65 + 68.8}{2}$ $or$ $x = \frac{-65 - 68.8}{2}$
$x = \frac{3.8}{2}$ $or$ $x = \frac{-133.8}{2}$
$x = 1.9$ $or$ $x = -66.9$

x + y = -65
  1.9 + y = -65
- 1.9   - 1.9
y = -66.9
  (x, y) = (1.9, -66.9)

or

  x + y = -65
  -66.9 + y = -65
+ 66.9 + 66.9
y = 1.9
  (x, y) = (-66.9, 1.9)

The two numbers that add up to -65 and can multiply to -126 are the numbers -66.9 and 1.9.

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