\(13.15+15.17+15.x=225\)

\(\Rightarrow15.\left(13+17+x\right)=225\)

\(\Rightarrow15.\left(30+x\right)=225\)

\(\Rightarrow30+x=\frac{225}{15}=15\)

\(\Rightarrow x=15-30\)

\(\Rightarrow x=-15\)

Vậy x = -15

13.15 + 15.17 + 15.x = 225

<=>  15( 13 + 17 + x ) = 225

<=> 13 + 17 + x = 225 : 15

<=> 30 + x        = 15

<=>      x            = 15 - 30

<=>       x           = -15

\(\left(x+1\right)^2-5=11\)

\(\Leftrightarrow\)\(\left(x+1\right)^2=16\)

\(\Leftrightarrow\left(x+1\right)^2=4^2\)

\(\Leftrightarrow x+1=4\)

\(\Leftrightarrow x=3\)

(x+1)² -5=11

(x+1)²=16

(x+1)²=(-+4)²

TH1:x+1=4    TH2:x+1=-4

=>x=3            =>x=(-4)-1

                      =>x=-5

phải có thêm dữ kiện mới lm đc chứ

chắc là tìm gtnn đấy

\(\left(138+21\right).51+159.\left(22+26\right)+1159\)

\(=159.51+159.48++159+1100\)

\(=159\left(51+48+1\right)+1100\)

\(=159.100+1100\)

\(=159.100+11.100\)

\(=\left(159+11\right).100\)

\(=170.100\)

\(=17000\)

(138+21)*51+159*(22+26)+1159

=159*51+159*48+1159

=159*(51+48)+1159

=159*99+1159

=15741+1159=16900

 mình ko biết có làm dúng ko bạn thử lại nhé

\(\left(135-7\right)\times5-135\times5+35\)

\(=135\times5-7\times5-135\times5+35\)

\(=135\times\left(5-5\right)-35+35\)

\(=0+0=0\)

\(\left(135-7\right).5-135.5+35\)

\(=\left(135-7-135\right).5+35\)

\(=-7.5+35\)

\(=0\)