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One of the solutions to the equation 5x2+bx+12=0 is − 4/5. Find the value of b.

1 Answer

2 votes

b = 19

substitute x = -
(4)/(5) into the equation and solve for b

5(-
(4)/(5))² -
(4)/(5) b + 12 = 0


(16)/(5) +
(60)/(5) =
(4)/(5) b


(76)/(5) =
(4)/(5) b

multiply both sides by 5 and divide by 4

b =
(76)/(4) = 19


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