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Musya8 [376]
3 years ago
12

Given the quadratic equation: f(x) = x2+4x-21

Mathematics
1 answer:
ryzh [129]3 years ago
6 0

Answer:

x = - 7, x = 3

Step-by-step explanation:

To find the x- intercepts let f(x) = 0 , that is

x² + 4x - 21 = 0

Consider the factors of - 21 which sum to give the coefficient of the x- term (+ 4)

The factors are + 7 and - 3, since

7 × - 3 = - 21 and 7 - 3 = + 4, then

x² + 4x - 21 = 0

(x + 7)(x - 3) = 0 ← in factored form

Equate each factor to zero and solve for x

x + 7 = 0 ⇒ x = - 7

x - 3 = 0 ⇒ x = 3

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Solve. Write the solution in interval notation. -2x>-8 and -5x<20.
Novosadov [1.4K]

Answer:

The interval notation of the solution is (-4 , 4)

Step-by-step explanation:

* Let us explain a very important point in solving inequality

- When you multiply or divide an inequality by negative number we

   must reverse the symbol of the inequality

- Ex:

∵ 2 < 3

- If we multiply the both sides of the inequality by -1, then the

  inequality will be -2 < -3 and this is completely wrong, so we must

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∴ -2 > -3

* Now let us solve the problem

∵ -2x > -8

- Divide both sides by -2 and remember to reverse the symbol of the

  inequality

∴ x < 4

∵ -5x < 20

- Divide both sides by -5 and remember to reverse the symbol of the

  inequality

∴ x > -4

- From both solutions

∴ -4 < x < 4

∴ The solution is {x : -4 < x < 4}

- Interval notation is a way of writing the solutions of inequalities

 ( , ) if x does not equal the end numbers

 [ , ] if x equals the end numbers

 [ , ) , ( , ] if x equals one of the two end numbers

* The interval notation of the solution is (-4 , 4)

4 0
3 years ago
(x + x - 8x? - 13x - 7) = (x + 2)
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Why is there a question mark?
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Use the number line to find (One-fourth) + (negative StartFraction 21 over 8 EndFraction) Negative StartFraction 19 over 4 EndFr
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Answer:

-\frac{19}{8}

Step-by-step explanation:

4 0
3 years ago
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