Question

Find the value of each given polynomial at the given value of its variable :
(i) $5x^2–7x+2$ at x = 2
(ii) $x^2+15x–4$ at x = -3
(iii) $3y+8–2y^2$ at y = –3
(v) $x^2+3x+1$ at x = -1/3
(v) $x^3–3x^2+5x+2$ at x = – 1

Answer 1

(i) The value of $5x^2–7x+2$ at x = 2 is $5(2{)}^2-7(2)+2$ = 20- 14 + 2 = 8.

(ii) The value of $x^2+15x–4$ at x = -3 is $(-3{)}^2+15(-3)-4$ = 9- 45 -4 = -40

(iii) The value of $3y+8–2y^2$ at y = –3 is 3 $(-3)+8–2(-3{)}^2$ = -9 + 8 -18 = -19

(v) The value of $x^2+3x+1$ at x = -1/3 is $(-\frac{1}{3}{)}^2+3(-\frac{1}{3})+1=\frac{1}{9}-1+1=\frac{1}{9}$

(v) The value of $x^3–3x^2+5x+2$ at x = – 1 is $(-1{)}^3-3(-1{)}^2+5(-1)+2$ = -1 -3 -5 +2 = -7.