math
posted by zumai on .
4. What are the coefficients in the polynomial 7x^2  4x + 6?
A. 7, 4
B. 7, 4, 6
C. 7, 4, 6
D. 7, 4
7. Suppose you earned 6t + 2 dollars on Monday and 9t  6 dollars on Tuesday. What were the total earnings? Simplify your answer.
A. 15t  4
B. 15t + 8
C. 3t  4
D. 3t + 8
15. (1.8 x 10^1)(7 x 10^5)
A. 1.26 x 10^7
B. 8.8 x 10^6
C. 8.8 x 10^5
D. 1.26 x 10^6***???
18. x(5x  4)
A. 4x^2  5x***???
B. 5x  4x
C. 5x + 4x
D. 5x^2 + 4x
im not sure about #4 and #7
i think #15 is D. not sure...
on #18 i keep getting 4x  5x^2
so A. is closest but i don't know why i keep getting this.
pls help asap!!!

4D
coefficients require a variable. The 6 is just a constant, not a coefficient of x.
7A
Total is just the sum:
6t+2 + 9t6 = (6+9)t+(26) = 15t4
15A
(1.8 x 10^1)(7 x 10^5)
= (1.8x7)x10^(1+5)
= 12.6x10^6
= 1.26x10^7
18D
x(5x4)
= x*5x x(4)
= 5x^2 + 4x
Look again at your answer. It is correct, but it is not A.