[tex](x^2+3)^2 + 7x^2+21=-10[/tex]
We want to convert this equation in terms of m, where [tex]m = x^2+3[/tex]
While solving this problem, I instantly noticed the [tex]x^2+3[/tex] in the first term of the equation. Replace that with m.
[tex]m^2 + 7x^2+21=-10[/tex]
Simplifying the rest is not as obvious. Using the distributive property, we can change [tex][7x^2+21][/tex] to [tex][7(x^2+3)][/tex]
Do you see the "m" in here? Look again if you don't.
Now we can simplify the equation to [tex]m^2 + 7m=-10[/tex] and this cannot be simplified further.
I'm always happy to help someone who appreciates the help! :D