4 years ago

What percentage of 9 th grade students can swim ?

Mathematics

1 answer:

fenix001 [56]4 years ago

6 0

I think it's 80% of students

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Is b = 15 a solution to the equation 4b - 20 = 40?

irina [24]

Answer:

yes

Step-by-step explanation:

4 x 15 - 20 = 40

60 - 20 = 40

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3 years ago

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The angles of a triangle are 989, 51°, and x®,<br> What is the value of x?

Anastaziya [24]

9514 1404 393

Answer:

x = 31

Step-by-step explanation:

The sum of angles in a triangle is 180°.

98° +51° +x° = 180°

x° = 31° . . . . . . . . . . . . subtract 149°

x = 31

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If x^2+1/x^2=3 find the value of x^2/(x^2+1)^2<br> Express answer as a common fraction.<br> Thanks!!

timama [110]

$x^2+\dfrac1{x^2}=3\implies x^4+1=3x^2\implies x^4-3x^2+1=0$

By the quadratic formula,

$x^2=\dfrac{3\pm\sqrt5}2\implies x^2+1=\dfrac{5\pm\sqrt5}2$

Then

$(x^2+1)^2=\dfrac{25\pm10\sqrt5+5}4=\dfrac{15\pm5\sqrt5}2$

$\implies\dfrac{x^2}{(x^2+1)^2}=\dfrac{\frac{3\pm\sqrt5}2}{\frac{15\pm5\sqrt5}2}=\dfrac{3\pm\sqrt5}{15\pm5\sqrt5}$

Multiply numerator and denominator by the denominator's conjugate:

$\dfrac{3\pm\sqrt5}{15\pm5\sqrt5}\cdot\dfrac{15\mp5\sqrt5}{15\mp5\sqrt5}=\dfrac{45\pm15\sqrt5\mp15\sqrt5-25}{15^2-(5\sqrt5)^2}=\dfrac{20}{100}=\dfrac15$

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3 years ago

Make b the subject of this formula. a=9b

USPshnik [31]

Answer:

a = 9b

divide each side by 9

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3 years ago

I don’t know how to do this for nothing

Vadim26 [7]

Answer:

Step-by-step explanation:

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