5b^2+39b=8 please solve and explain why

Step-by-step explanation:

5b²+39b=8

<=> 5b²+39b-8=0

(5b-1)(b+8)=0

b = ¹/5 or b = -8

b=-8 and b=1/5.

Solution given:

5b²+39b=8

5b²+39b-8=0

try to do middle term factorization.

it needs 40 while multiplication and 39 when subtraction.

it is 40-1 and 40*1

now

doing middle term factorization

5b²+(40-1)b-8=0

5b²+40-b-8=0

take common from each 2 term

5b(b+8)-1(b+8)=0

again take common and keep remaining in another brackets

(b+8)(5b-1)=0

either

b=-8

or

b=1/5