Toán Lớp 6: -3. (x+5)+7.(x+3)=18 45.(x+2)-15.(x+2)-20.x=120

Question

Toán Lớp 6:  -3. (x+5)+7.(x+3)=18 45.(x+2)-15.(x+2)-20.x=120

aivilanlan · Answer

-3. ( x + 5 ) + 7. ( x + 3 ) = 18   $ Rightarrow$ -3x - 15 + 7x + 21 = 18   $ Rightarrow$ ( 7x - 3x ) + ( -15 + 21 ) = 18   $ Rightarrow$ 4x + 6 = 18   $ Rightarrow$ 4x = 18 - 6   $ Rightarrow$ 4x = 12   $ Rightarrow$ x = 12 : 4   $ Rightarrow$ x = 3     $Vậy$ x = 3   $ text{ _______________________________ }$   45. ( x + 2 ) - 15. ( x + 2 ) - 20. x = 120   $ Rightarrow$ ( x + 2 ). ( 45 - 15 ) - 20x = 120   $ Rightarrow$ 30. ( x + 2 ) - 20x = 120   $ Rightarrow$ 30x + 60 - 20x = 120   $ Rightarrow$ x. ( 30 - 20 ) = 120 - 60   $ Rightarrow$ 10x = 60   $ Rightarrow$ x = 60 : 10   $ Rightarrow$ x = 6        $Vậy$ x = 6

hienchaudiem · Answer

Giải đáp:       Lời giải và giải thích chi tiết:   $-3.(x+5)+7.(x+3)=18^{}$   $ Rightarrow$ $-3.(x+5)+7.(x+3)=2.(2x+3)^{}$   $ Rightarrow$ $2.(2x+3)=2.3^{2}$    $ Rightarrow$ $4x+6=18^{}$    $ Rightarrow$ $4x=12^{}$    $ Rightarrow$ $x=12:4^{}$    $ Rightarrow$ $x=3^{}$       $45.(x+2)-15.(x+2)-20.x=120^{}$   $ Rightarrow$ $45.(x+2)-15.(x+2)+(-20).x=10.(x+6)^{}$    $ Rightarrow$ $10.(x+6)=^{}$ $2^{3}$$.3.5^{}$    $ Rightarrow$ $10x+60=120^{}$    $ Rightarrow$ $10x=60^{}$    $ Rightarrow$ $x=60:10^{}$    $ Rightarrow$ $x=6^{}$     Hok tốt !!!