Toán Lớp 8: 3x(12x – 4) – 9x(4x – 3) = 30
b) x(5 – 2x) + 2x(x – 1) = 15
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Toán Lớp 8: 3x(12x – 4) – 9x(4x – 3) = 30
b) x(5 – 2x) + 2x(x – 1) = 15
Comments ( 2 )
a)3x(12x – 4) – 9x(4x – 3) = 30
36x^2-12x-36x^2+27x = 30
15x=30
x=2
Vậy x=2
b) x(5 – 2x) + 2x(x – 1) = 15
5x – 2x^2 + 2x^2 – 2x = 15
3x = 15
x=5
Vậy x=5
Answer
a, 3x . (12x – 4) – 9x . (4x – 3) = 30
=> 3x . 12x – 3x . 4 – 9x . 4x + 9x . 3 = 30
=> 36x^2 – 12x – 36x^2 + 27x = 30
=> (36x^2 – 36x^2) + (27x – 12x) = 30
=> 15x = 30
=> x = 30 : 15
=> x = 2
Vậy x = 2
____________________________
b, x . (5 – 2x) + 2x . (x – 1) = 15
=> x . 5 – x . 2x + 2x . x – 2x . 1 = 15
=> 5x – 2x^2 + 2x^2 – 2x = 15
=> (5x – 2x) + (2x^2 – 2x^2) = 15
=> 3x = 15
=> x = 15 : 3
=> x = 5
Vậy x = 5