(4t³ + 2t² - 7t + 5) + (5t⁴ + 3t³ + 4t - 7) = 4t³ + 2t² - 7t + 5 + 5t⁴ + 3t³ + 4t - 7  =

 5t⁴ + 4t³ + 3t³ + 2t² - 7t +4t + 5 + (-7) = 5t⁴ + 7t³ + 2t² - 3t + (-2) = 5t⁴ + 7t³ + 2t² - 3t -2

Notice that 5t⁴  and 2t² are the only terms with an exponent of 4 and one with an exponent of 2 in the problem and hence cannot be combined with (meaning added to)  another term.     return