Question

Write the quadratic equation in standard form and then choose the value of "b." (2x - 1)(x + 5) = 0

Answer 1

if we were to foil
after experieence

we know
ax²+bx+c=0

and
in form
(ax+b)(cx+d)=0
if we expand it, we get
acx²+bcx+adx+bd=0
or
(ac)x²+(bc+ad)x+(bd)=0
compare to
ax²+bx+c=0
we notice that the middle terms (x terms) are

b=(bc+ad)
so

in form
(2x-1)(1x+5)
b=bc+ad=(-1*1+2*5)=-1+10=9

b=9
or you could just expand it