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Answer:
-10, -8
Step-by-step explanation:
a + b = -18
a * b = 80
Solve:
from the first eq.
a = 18 - b
replacing this value in the secon eq.
(18-b)*b = 80
18*b + b*-b = 80
-b² + 18b = 80
-b² + 18b - 80 = 0
b = {-18±√((18)² - (4*-1*-80))] /(2*-1)
b = {-18±√(324.320)} / -2
b = {-18±√4} / -2
b = {-18±2} / -2
b₁ = {-18-2} / -2 = -20/-2 = 10
b₂ = {-18+2} / -2 = -16/-2 = 8
The two number must be negatives, so the numbers are:
-10 and -8
Check:
-10 + (-8) = -10 - 8 = -18
-10*-8 = 80