Like Terms are the terms which have same algebraic factors. They must have the same variable with the same exponent.
Unlike Terms are the terms which have different algebraic factors.
2x2 + 3x – 5 does not contain any term with same variable.
2a2 + 3a2 + 7a – 7 contains two terms with same variable i.e. 2a2 and 3a2, so these are like terms .