1) = (-4 + -6) +(440 -440)

  = -10

2) = (-56 - 64) + 263 + 483

  = -120 +  746 = -626

3) =(329 - 329) +64 +30 = 94

4) = (23 - 23) -10 = -10

5) =(215 -215) + 18 = 18

P2O5 + 3H2O -> 2H3PO4

Ca + 2H2) -> Ca(OH)2 + H2

K2O + H2O -> 2KOH

2Al + 6HCl -> 2AlCl3 + 3H2

lộn dấu :>

Na2O ; BrO2 ; Al2O3 ; SO2 ;SO3 ; SO4; P2O5 ; NO3 ; FeO ; Fe2O3 ; Fe3O4

KOH ; Ba(OH)2 ; Ca(OH)2 ; NaOH

H2O ; H2SO3; HNO3 ; H2SO4 ; H2PO4

cái cuối là H2O

Mg + 2HCl -> MgCl2 + H2

MgCl2 + 2H2O -> Mg(OH)2 + 2HCl

Mg(OH)2 -> MgO + H2O

MgO + 2HNO3 -> Mg(NO3)2 + H2)

<=> \(\left(x-5\right)\left(4x-x+5\right)=0\)

<=>\(\left(x-5\right)\left(3x-5\right)=0\)

=>\(\left\{{}\begin{matrix}x-5=0\\3x-5=0\end{matrix}\right.=>\left\{{}\begin{matrix}x=5\\x=\dfrac{3}{5}\end{matrix}\right.\)