rút gọn a)3*(x^2-7)-x*(3x+5) b)(x+3)*(x-3)-x*(23+x) c)(x+5)*(x-2)-(x+2)*(x+7) 07/08/2021 Bởi Brielle rút gọn a)3*(x^2-7)-x*(3x+5) b)(x+3)*(x-3)-x*(23+x) c)(x+5)*(x-2)-(x+2)*(x+7)
Giải thích các bước giải: $a.3(x^2-7)-x(3x+5)=3x^2-21-(3x^2+5x)=-21-5x$ $b.(x+3)(x-3)-x(23+x)=x^2-9-(x^2+23x)=-9-23x$ $\begin{split}c.(x+5)(x-2)-(x+2)(x+7)&=x^2-2x+5x-10-(x^2+7x+2x+14)\\&=-6x-24\end{split}$ Bình luận
`*` `3*(x^2-7)-x*(3x+5)` `<=>3x^2-21-3x^2-5x` `<=>-21-5x` `*` `(x+3)*(x-3)-x*(23+x)` `<=>x^2-9-23x-x^2` `<=>-6-23x` `*` `(x+5)*(x-2)-(x+2)*(x+7)` `<=>x^2-2x+5x-10-x^2-7x-2x-14` `<=>-6x-24` Bình luận
Giải thích các bước giải:
$a.3(x^2-7)-x(3x+5)=3x^2-21-(3x^2+5x)=-21-5x$
$b.(x+3)(x-3)-x(23+x)=x^2-9-(x^2+23x)=-9-23x$
$\begin{split}c.(x+5)(x-2)-(x+2)(x+7)&=x^2-2x+5x-10-(x^2+7x+2x+14)\\&=-6x-24\end{split}$
`*` `3*(x^2-7)-x*(3x+5)`
`<=>3x^2-21-3x^2-5x`
`<=>-21-5x`
`*` `(x+3)*(x-3)-x*(23+x)`
`<=>x^2-9-23x-x^2`
`<=>-6-23x`
`*` `(x+5)*(x-2)-(x+2)*(x+7)`
`<=>x^2-2x+5x-10-x^2-7x-2x-14`
`<=>-6x-24`