(2x+5)(x-4) my calulater got 150, but I don't know how it worked the problem. Can someone show how to work this out?

Question

(2x+5)(x-4) my calulater got 150, but I don't know how it  worked the problem. Can someone show how to work this out?

anonymous · Answer

your calculator may not understand variables

anonymous · Answer

you should do four multiplications, sometimes denoted by the unfortunate mnemonic device "FOIL' for "first, outer inner last" 
or just multiply as you would for two 2 digit numbers

anonymous · Answer

I'll try that.

anonymous · Answer

good

anonymous · Answer

I haven't done foil in a long time. I think I messed up. so far i have 2x^2+3x/x=-1/3. can you show how to foil this?

anonymous · Answer

so far i have
2x^2-2x+5x+1=
2x^2+3x+1=
2x^2+3x=-1
2x^2+3x/3=-1/3
I don't know where to go from here

anonymous · Answer

Is your equation equal to zero?