Question

Someone check my answers please?
Multiply or find the special product:
1. (7x-2)(4x-3)
my answer: 28x^2-29x+6
2. (4a+5b)(4a-5)
m answer: 16a^2-25b^2
3. (x^2-x+1)(x^2-3x-2)
my answer: x^4-4x^3+2x^2-x-2
4. (5+sqrt x)(5-sqrt x)
my answer: 25-x
Thank you!

Answer 1

(7x-2)(4x-3)
7x(4x-3)-2(4x-3)
28x^2-21x-8x+6
28x^2-29x+6

Correct!

Answer 2

Thank you!! Do you know if the other ones are right as well??

Answer 3

(4a+5b)(4a-5)
4a(4a-5)5b(4a-5)
16a^2-20a+20ab-25b

Answer 4

aww...I knew there had to be a typo somewhere! #2 is supposed to be (4a+5b)(4a-5b)

Answer 5

I just checked the rest of them and i'm pretty sure they are all right! Yay! Thank you for your help! :)

Answer 6

\(\huge \color{red}{\text{FOIL}}\)

\(\color{red}{F}irst\)
\(\color{red}{O}uter\)
\(\color{red}{I}nner\)
\(\color{red}{L}ast\)

\((ax+b)(cx+d)=acx^2+adx+bcx+bd\)

\((7x-2)(4x-3)=(7x\times4x)+(3\times7x)+((-2)\times4x)+((-2)\times(-3))\)

\(=28x^2-29x+6\)

As long as you have down that basic form you should be alright. :)