Answer:
(b) 3 terms, degree 10
Explanation:
When simplifying polynomials, the first thing you look at is the exponents of the variables in each term. (The terms are separated by + or - signs.) Only terms with the same set of exponents can be combined.
When considering the degree of the polynomial, you look at the sum of exponents of the variables in each term. That sum is the degree of the term. The degree of the polynomial is the highest of the degrees of the terms.
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exponents and degree
The four terms have variables s and t. If we write the exponents of those variables as an ordered pair, we will have one ordered pair for each term:
5s⁶t² ⇒ (exponent of s, exponent of t) ⇒ (6, 2); degree = 6+2 = 8
6st⁹ ⇒ (1, 9); degree = 1+9 = 10
-8s⁶t² ⇒ (6, 2); degree 6+2 = 8 (this is a like term to the first term)
-6t⁷ ⇒ (0, 7); degree 0+7 = 7
The degrees are 8, 10, 8, 7, so the highest degree is 10. This is the degree of the polynomial.
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combining terms
We can only combine the terms containing s⁶t². Doing that gives ...
(5 -8)s⁶t² +6st⁹ -6t⁷ = -3s⁶t² +6st⁹ -6t⁷ . . . . . three terms
In "standard form", the terms are written in order of decreasing degree:
6st⁹ -3s⁶t² -6t⁷ . . . . . . 3 terms, degree 10