Question

Select all of the expressions equivalent to (m + m)(−4.2m).
2m(−4.2m)
−4.2m3
−2.2m2
4.2m2 + 4.2m2
−4.2m2 + (−4.2m2)
−8.4m2

Answer 1

Equivalent expressions:
- 2m(−4.2m) — because (m+m)=2m, so 2m(−4.2m)=−8.4m^2.
- −4.2m^2 + (−4.2m^2) — combines to −8.4m^2.
- −8.4m^2 — exactly the simplified form.

Not equivalent: −4.2m^3 (wrong power), −2.2m^2 (wrong coefficient), 4.2m^2+4.2m^2 (=+8.4m^2, wrong sign).