How many real solutions does x²+8x+20=0 have?
1 answer:
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Answer:
- The smaller one is x = 3
- and the larger one is x = 6
Step-by-step explanation:
A "critical number" is a function argument where the function has zero or undefined slope. A polynomial function never has undefined slope, so we're looking for the x-values where f'(x) = 0.
A graphing calculator easily shows the points that have zero slope. They are found at x = 3 and x = 6.
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Setting the derivative to zero is another way to find the points with zero slope:
f'(x) = 6x^2 -54x +108 = 6(x^2 -9x +18) = 6(x-3)(x-6)
The derivative will be zero where the factors are zero, at x=3 and x=6.
The critical numbers are x=3 and x=6.
