Answer:
(c) x = 0.39 and x = -3.89
Explanation:
You want the solutions to the quadratic equation ...
2x² +7x = 3.
Root relations
The roots of the equation ...
x² +bx +c = 0
have a sum of -b and a product of c.
Subtracting 3 and dividing the equation by 2, we have ...
2x² +7x -3 = 0 . . . . . . . . subtract 3
x² +3.5x -1.5 = 0 . . . . . . divide by 2
This tells us the sum of the roots is -3.5.
Answer choice C has that sum: x = 0.39, x = -3.89.
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Additional comment
The sums of the answer choices are ...
0.60 -2.60 = -2.00
-0.60 +2.60 = 2.00
0.39 -3.89 = -3.50
-0.39 +3.89 = 3.50
Sometimes, checking the offered choices is the simplest way to find the answer.
Here, checking the sum gives the best discriminator of right from wrong. The products are all near -1.5, so that is less helpful.
We can see the relation by considering the factored form:
(x -p)(x -q) = x² -(p+q)x +pq . . . . . . where p and q are the roots
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