9514 1404 393
Answer:
b = -8, 2.5
Step-by-step explanation:
The equation can be rewritten to standard form:
2b² +11b -40 = 0
In this form, it can be factored by looking for factors of (2)(-40) that have a total of +11.
-80 = 80(-1) = 40(-2) = 20(-4) = 16(-5) = 10(-8)
The factors 16 and -5 total 11, so we can now write the equation in a form suitable for factoring by grouping:
2b² +16b -5b -40 = 0 . . . . write the b term using the numbers we found
2b(b +8) -5(b +8) = 0 . . . . factor pairs of terms
(2b -5)(b +8) = 0 . . . . . . . . finish the factoring
Solutions are values of b that make these factors zero:
2b -5 = 0 ⇒ b = 5/2
b +8 = 0 ⇒ b = -8
Solution to the equation are b = -8 and b = 5/2.
