Question

Please need help in these 3 algebra questions !!!!

7. Add: (3s2 + 7s + 2) + (5s2 + 9s – 1)

A. 8s2 + 16s + 3

B. 8s4 + 16s + 1

C. 8s2 + 16s + 1
D. –2s2 – 2s + 1
8. (–3t2u3)(5t7u8) = _______.

A. –15t14u24

B. 2t9u11

C. –15t–5u–5

D. –15t9u11
11. The square of a number is equal to 6 more than the number. Find all such numbers.

A. –4; –3

B. –2

C. 3; –2

D. –3

Answer 1

`\large\boxed{7.\ B.\ 8s^2+16s+1}\\\\\boxed{8.\ D.\ -15t^9u^(11)}\\\\\boxed{11.\ C.\ 3,\ -2}`

Explanation:

`7.\\(3s^2+7s+2)+(5s^2+9s-1)=3s^2+7s+2+5s^2+9s-1\\\\\text{combine like terms}\\\\=(3s^2+5s^2)+(7s+9s)+(2-1)\\\\=8s^2+16s+1`

`8.\\(-3t^2u^3)(5t^7u^8)=(-3\cdot5)(t^2t^7)(u^3u^8)\qquad\text{use}\ a^na^m=a^(n+m)\\\\=-15t^(2+7)u^(3+8)=-15t^9u^(11)`

`11.\\n-the\ number\\\\n^2=n+6\qquad\text{subtract}\ n\ \text{and}\ 6\ \text{from both sides}\\\\n^2-n-6=0\\\\n^2+2n-3n-6=0\\\\n(n+2)-3(n+2)=0\\\\(n+2)(n-3)=0\iff n+2=0\ \vee\ n-3=0\\\\n+2=0\qquad\text{subtract 2 from both sides}\\n=-2\\\\n-3=0\qquad\text{add 3 to both sides}\\n=3`