Tìm x: c) −7(3x – 5) + 2(7x – 14) = 28; d) 5(3 – 2x) + 5(x – 4) = 6 – 4x.
Giải thích
c) −7(3x – 5) + 2(7x – 14) = 28
−21x + 35 + 14x – 28 = 28
−7x = 28 – 7
−7x = 21
x = −3
Vậy x = −3
d) 5(3 – 2x) + 5(x – 4) = 6 – 4x
15 – 10x + 5x – 20 = 6 – 4x
−5x + 4x = 6 + 5
−x = 11
x = −11
Vậy x = −11