First we must simplify the left side.
-20x² - 30x = 21
We need to move 21 to the left side of the problem, to do that we need to subtract both sides:
-20² - 30x - 21 = 0
Factor -1 out of -20x² - 30x - 21.
So then we have:
- (20x² + 30x + 21) = 0
Our set is: 20x² + 30x + 21 equal to 0 now we must solve for x.
To do that we need to divide.
x = -15 = √195
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20