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Toán Lớp 8: a) ( x – 1 ) ( 2x + 3 ) – 2x ² = 7 b) x ² – 2021x – x + 2021 = 0

Home/ Toán Lớp 8: a) ( x – 1 ) ( 2x + 3 ) – 2x ² = 7 b) x ² – 2021x – x + 2021 = 0

Toán Lớp 8: a) ( x – 1 ) ( 2x + 3 ) – 2x ² = 7 b) x ² – 2021x – x + 2021 = 0

Kiều Nguyệt Tháng Chín 6, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: a) ( x – 1 ) ( 2x + 3 ) – 2x ² = 7
b) x ² – 2021x – x + 2021 = 0

Comments ( 1 )

behocgioitoan
6 Tháng Chín, 2022 at 5:08 sáng

Reply

Giải đáp:

$a) (x-1).(2x+3)-2x²=7$

$⇔ 2x²+3x-2x-3-2x²=7$

$⇔ (2x²-2x²)+(3x-2x)-3=7$

$⇔ x-3=7$

$⇔ x=10$

$Vậy$ $x=10$

$x²-2021x-x+2021=0$

$⇔ x.(x-2021)-(x-2021)=0$

$⇔ (x-1).(x-2021)=0$

$⇔$ \(\left[ \begin{array}{l}x-1=0\\x-2021=0\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=1\\x=2021\end{array} \right.\)

$\text{Vậy x ∈ {1;2021}}$

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