Answer:
[tex]\Huge\boxed{15x^3+26x^2-3x+42}[/tex]
Step-by-step explanation:
[tex]\text{Use FOIL:}\\\\(a+b)(c+d)=ac+ad+bc+bd[/tex]
[tex](3x + 7)(5x^2-3x + 6)\\\\=(3x)(5x^2)+(3x)(-3x)+(3x)(6)+(7)(5x^2)+(7)(-3x)+(7)(6)\\\\=15x^3-9x^2+18x+35x^2-21x+42\\\\\text{combine like terms}\\\\=15x^3+(-9x^2+35x^2)+(18x-21x)+42\\\\=15x^3+26x^2-3x+42[/tex]
