do you know how to start? you will have to do 4 multiplications
4 ? multiplications ?
they are \[5x\times 5x\] \[5x\times -8\] \[-2\times 5x\] \[-2\times -8\]
it's called foil.....First Outer Inner Last 5x^2 x 5x^2 = 25x^2 is the First Outer is 5x^2 x -8 = -40x Inner is -2 x 5x = -10x Last is -2 x -8 = 16 now combine like terms : 25x^2 -5x + 16
you get \[25x^2\] \[-40x\] \[-10x\] \[16\]
for a total of \[25x^2-40x-10x+16\] combine like terms to get \[25x^2-50x+16\]
i yam what i yam!
oh ok i understand
it is harder with polynomials but if you were going to multiply 12 by 23 you would do 4 multiplications right?
1 2 x 23 ______ 3 6 2 4
really it is identical
you would do 4 multiplications and one addition
polynomials work exactly the same way
you could even write it the same way if you like. you just have to be careful of the signs
5x - 2 5x - 8 ____________ -40x +16 25x^2 -10x 25x^2 -50x +16
but with polynomials most people write it from the top down instead of from the bottom up like we do with numbers. there is no carrying with polynomials. that is why