Question

If x = -5, what is the value of 7 - x(2x + 1)?

Answer 1

By using substitution you end up with -48

Answer 2

First write the polynomial

`\qquad\quad {:}\longrightarrow\sf 7-x (2x+1)`

• Simplify

`\qquad\quad {:}\longrightarrow\sf 7-2x^3-x`

• Substitute the value of x=-5

`\qquad\quad {:}\longrightarrow\sf 7-2 (-5)^3- (-5)`

`\qquad\quad {:}\longrightarrow\sf 7-250 +5`

`\qquad\quad {:}\longrightarrow\sf -238`