Question 234·Hard·Advanced Math

Equivalent expressions agree for every $x$, so you may choose $x=0$. Choose an input that removes $x$ without removing the unknown. Here, $b(4-x)$ becomes $4b$, while the other terms containing $x$ become $0$. Substitute $0$ on both sides: $6(0)^2+b(4-0)-3(0)(b-2)=6(0)^2+14(0)-8$. Don't choose $x=1$: the terms containing $b$ become $3b-3b=0$, so that input can't reveal $b$.

Type $6(0)^2+b(4-0)-3(0)(b-2)\sim6(0)^2+14(0)-8$. The regression symbol $\sim$ tells Desmos to find the value of $b$ that makes the two outputs equal. Under PARAMETERS, Desmos reports $b=-2$. So the constant is $-2$. Choice B.