Toán a: 5x.(3+x) – 5x.(x+7) =40 b:(4-x)(x+2) = 0 c:2x – 36 = 48-x 04/07/2021 By Elliana a: 5x.(3+x) – 5x.(x+7) =40 b:(4-x)(x+2) = 0 c:2x – 36 = 48-x
`\text{a)}` `5x(3+x) – 5x(x+7) = 40` `-> 5x(3+x – x – 7) =40` `-> 5x . -4 = 40` `-> 5x = 40 : (-4) =-10` `-> x = -10 : 5` `-> x = -2` Vậy `x = -2` `\text{b)}` `(4-x)(x+2) =0` `->` \(\left[ \begin{array}{l}4-x =0\\x+2 =0\end{array} \right.\) `->` \(\left[ \begin{array}{l}x=4\\x=-2\end{array} \right.\) Vậy `x \in {4 ; -2}` `\text{c)}` `2x -36 = 48 -x` `-> 2x +x = 48 +36` `-> 3x = 84` `-> x = 84/3` `-> x= 28` Trả lời
Đáp án: a, `5x . (3 + x) – 5x . (x + 7) = 40` `5x . ( 3 + x – x – 7) = 40` `5x . (-4) =40` `5x = 40 : (-4) = (-10)` ` x = (-10) : 5 = (-2)` b, `(4 – x)( x + 2) = 0` ⇒\(\left[ \begin{array}{l}4 – x = 0\\x + 2 = 0\end{array} \right.\) ⇒\(\left[ \begin{array}{l}x=4\\x=-2\end{array} \right.\) `text{ Vậy x ∈{ 4 ; -2}}` c, `2x – 36 = 48 – x` `2x + x = 48 + 36` `3x = 84` ` x = 84 : 3 = 28` Trả lời
`\text{a)}`
`5x(3+x) – 5x(x+7) = 40`
`-> 5x(3+x – x – 7) =40`
`-> 5x . -4 = 40`
`-> 5x = 40 : (-4) =-10`
`-> x = -10 : 5`
`-> x = -2`
Vậy `x = -2`
`\text{b)}`
`(4-x)(x+2) =0`
`->` \(\left[ \begin{array}{l}4-x =0\\x+2 =0\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=4\\x=-2\end{array} \right.\)
Vậy `x \in {4 ; -2}`
`\text{c)}`
`2x -36 = 48 -x`
`-> 2x +x = 48 +36`
`-> 3x = 84`
`-> x = 84/3`
`-> x= 28`
Đáp án:
a, `5x . (3 + x) – 5x . (x + 7) = 40`
`5x . ( 3 + x – x – 7) = 40`
`5x . (-4) =40`
`5x = 40 : (-4) = (-10)`
` x = (-10) : 5 = (-2)`
b, `(4 – x)( x + 2) = 0`
⇒\(\left[ \begin{array}{l}4 – x = 0\\x + 2 = 0\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x=4\\x=-2\end{array} \right.\)
`text{ Vậy x ∈{ 4 ; -2}}`
c, `2x – 36 = 48 – x`
`2x + x = 48 + 36`
`3x = 84`
` x = 84 : 3 = 28`