Question

Let N be the number of quadratic equations with coefficients from {0, 1, 2, 3...., 9} such that 0 is a solution of each equation. Then the value of N is 

(A) 2⁹ 

(B) infinite 

(C) 90 

(D) 900

Answer 1

Correct option (C) 90

Explanation:

Since 0 is a solution, equation must be of the form ax² + bx = 0,

where a ∈ {1, 2, 3, 4, 5, 6, 7, 8, 9} and b ∈ {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

∴ a has 9 choices and b has 10 choices

⇒ N = 9 × 10 = 90