Toán Lớp 7: tìm x biết -4x(x-5)-2x(8-2x)=-3
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 7: tìm x biết -4x(x-5)-2x(8-2x)=-3
Comments ( 2 )
Answer
-4x . (x – 5) – 2x . (8 – 2x) = -3
=> -4x . x + 4x . 5 – 2x . 8 + 2x . 2x = -3
=> -4x^2 + 20x – 16x + 4x^2 = -3
=> (4x^2 – 4x^2) + (20x – 16x) = -3
=> 4x = -3
=> x = -3 : 4
=> x = -3/4
Vậy x = -3/4
-4x ( x – 5 ) – 2x ( 8 – 2x ) = – 3
⇒ [ – 4x^2 – ( – 20 )x ] – ( 16x – 4x^2 ) = – 3
⇒ – 4x^2 + 20x – 16x + 4x^2 = – 3
⇒ ( – 4x^2 + 4x^2 ) + ( 20x – 16x ) = – 3
⇒ 0 + 4x = – 3
⇒ 4x = – 3
⇒ x = – 3 : 4
⇒ x = – 3/4
Vậy , x = – 3/4 .