Classify the following as linear, quadratic and cubic polynomials:

(i) x² + x

(ii) x - x³

(iii) y + y² + 4

(iv) 1 + x

(v) 3t

(vi) r²

(vii) 7x³

(i) x² + x — Quadratic polynomial [∵ Degree is 2]

(ii) x - x³ — Cubic polynomial [∵ Degree is 3]

(iii) y + y² + 4 — Quadratic polynomial [∵ Degree is 2]

(iv) 1 + x — Linear polynomial [∵ Degree is 1]

(v) 3t — Linear polynomial [∵ Degree is 1]

(vi) r² — Quadratic polynomial [∵ Degree is 2]

(vii) 7x³ — Cubic polynomial [∵ Degree is 3]