Best solutions to - "What is x if −4x+9x=−30?"

Seelakant6vr

Answered question

2022-02-02

What is x if

- 4 x + \frac{9}{x} = - 30

Nathen Lamb

Beginner2022-02-03Added 13 answers

Explanation:
Multiply both sides of the equation by

x \to - 4 x^{2} + 9 = - 30 x

y = - 4 x^{2} + 30 x + 9 = 0

D = b^{2} = b^{2} - 4 a c = 900 + 144 = 1044 = 36 (29) \to d = \pm 6 \sqrt{29}

There are 2 real roots:

x = - \frac{b}{2 a} \pm \frac{d}{2 a} = - \frac{30}{- 8} \pm \frac{6 \sqrt{29}}{8} = \frac{15 \pm 3 \sqrt{29}}{4}

liofila3w7

Beginner2022-02-04Added 13 answers

The fact that x is in the denominator already means that we assume it is not equal to 0.
Multiply all the terms by x to get rid of the fraction.

x \times - 4 x + \frac{x \times 9}{x} = x \times - 30

- 4 x^{2} + 9 = - 30 x

re-arrange and make

= 0

0 = 4 x^{2} - 30 x - 9

does not factorise
Use the formula:

a = 4, b = - 30, c = - 9

x = \frac{- b \pm \sqrt{b^{2} - 4 a c}}{2 a}

x = \frac{(- (- 30) \pm \sqrt{{(- 30)}^{2} - 4 (4) (- 9)}} {2 (4)}}{}

x = (\frac{30 \pm \sqrt{900 + 144}}{8})

x = \frac{30 \pm \sqrt{1044}}{8}

Answer:

x = 7.7889 or x = - 0.2889

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