make one side zero
add 59x to both sides
8x^2+59x+21=0
factor
to find the factor in
ax^2+bx+c form when a>1
multiply a and c together
find what 2 numbers add up to b and multiply to ac so
a=8
b=59
c=21
ac=8 times 21=168
factors that add up to 59 and multiply to get 168
the numbers are 56 and 3
3 and 56 are the numbers since 3 times 56=168 and 3+56=168 so
split it up
8x^2+56x+3x+21=0
group
(8x^2+56x)+(3x+21)=0
undistribute
(8x)(x+7)+(3)(x+7)=0
reverse distribute
(8x+3)(x+7)=0
set each to zero
8x+3=0
subtract 3
8x=-3
divide by 8
x=-3/8
x+7=0
subtract 7
x=-7
x=-7 or -3/8
