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joja [24]
3 years ago
12

Solve the equation for x, where x is a real number (5 points): -2x^2 + 7x + 21 = 16

Mathematics
1 answer:
Sveta_85 [38]3 years ago
5 0
Subtract 16 to both sides to the equation becomes -2x^2 + 7x + 5 = 0.

To solve this equation, we can make use of the quadratic formula. The quadratic formula solves equations of the form ax^2 + bx + c = 0
                                  x = [ -b ± √(b^2 - 4ac) ] / (2a)
                                  x = [ -7 ± √(7^2 - 4(-2)(5)) ] / ( 2(-2) )
                                  x = [ -7 ± √(49 - (-40) ) ] / ( -4 )
                                  x = [ -7 ± √(89) ] / ( -4)
                                  x = [ -7 ± sqrt(89) ] / ( -4 )
                                  x = 7/4 ± -sqrt(89)/4
The answers are 7/4 + sqrt(89)/4 and 7/4 - sqrt(89)/4.
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Step-by-step explanation:

The given is:

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Let us solve this problem by using the ratio method

∵ George deleted 63 songs from his MP 3 player

∵ The ratio of songs he deleted to the songs he kept was 7 : 4

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→  7                :    4          :    11 (7 + 4 = 11)

→  63             :                 :    x

By using cross multiplication

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