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3 years ago

Find the value of 9x - 7 given that -2x - 7 = 3.

Mathematics

1 answer:

r-ruslan [8.4K]3 years ago

8 0

-2x-7=3

or,-2x=10

or,x=-5

Since we`ve got the value of x.let`s substitute it in 9x-7

=9×(-5)-7

=-52

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2x²-5x-12=0 (simplify solution set)

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Answer:

x = 4 or x = -3/2

Step-by-step explanation:

To simplify and solve this, let's use the quadratic formula.

So the format of a quadratic equation is supposed look like this:

$ax^2+bx+c=0$

Let's find a, b, c:

a is the coefficient of x^2
b is the coefficient of x
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Now let's solve the equation.

Let's solve your equation step-by-step.

2x^2−5x−12=0

For this equation: a=2, b=-5, c=-12

2x^2+−5x+−12=0

Step 1: Use quadratic formula with a=2, b=-5, c=-12.

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$x=\frac{-(-5)\pm\sqrt{(-5)^2-4(2)(-12)} }{2(2)}$

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$x=4$ or $x=\frac{-3}{2}$

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<u>Answer:</u>

x = 4 or x = -3/2

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Statistics students in Oxnard College sampled 10 textbooks in the Condor bookstore, and recorded number of pages in each textboo

jeka94

Answer:

y = -0.85 + 0.09x; $49.82

Step-by-step explanation:

1. Calculate Σx, Σy, Σxy, and Σx²

The calculation is tedious but not difficult.

$\begin{array}{rrrr}\mathbf{x} & \mathbf{y} & \mathbf{xy} & \mathbf{x^{2}}\\526 & 52.08 & 27394.08 & 276676\\625& 59.00 & 36875.00 &390625\\589 & 56.12 & 33054.68 & 346921\\409 & 25.72 & 10519.48 & 167281\\489 & 34.12& 16684.68 & 293121\\500 & 53.00 & 26500.00 &250000\\906 & 76.48 & 71102.88 & 820836\\251 &26.08 & 6546.08 & 63001\\595 & 50.60 & 30107.00 & 354025\\719 & 68.52 & 49265.88 & 516961\\\mathbf{5609} & \mathbf{503.72} &\mathbf{308049.76} & \mathbf{3425447}\\\end{array}$

2. Calculate the coefficients in the regression equation

$a = \dfrac{\sum y \sum x^{2} - \sum x \sum xy}{n\sum x^{2}- \left (\sum x\right )^{2}} = \dfrac{503.7 \times 3425447 - 5609 \times 308049.76}{10 \times 3425447- 5609^{2}}\\\\= \dfrac{1725466163 - 1727851103.84}{34254470 - 31460881} = -\dfrac{2384941}{2793589}= \mathbf{-0.8537}$

$b = \dfrac{n\sumx y - \sum x \sumxy}{n\sum x^{2}- \left (\sum x\right )^{2}} = \dfrac{3080498 - 2825365.48}{2793589} = \dfrac{255132}{2793589} = \mathbf{0.09133}$

To two decimal places, the regression equation is

y = -0.85 + 0.09x

3. Prediction

If x = 563,

y = -0.85 + 0.09x = -0.85 + 0.09 × 563 = -0.85 + 50.67 = $49.82

(If we don't round the regression equation to two decimal places, the predicted value is $50.56.)

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3 years ago