Explanation

Cost of 120 copies = Rs. 6000

Cost of 1 copy = Rs. 6000 / 120

= Rs. 50

Cost of 400 copies = Rs. 50 × 400

= Rs. 20000

Explanation

Given y ∝ x, we can write y = kx.

When x = 5, y = 210:

210 = k(5)

k = 210/5

k = 42

Now, when x = 2:

y = kx

y = 42(2)

y = 84

Explanation

Arthur Cayley, a British mathematician, introduced the modern concept of matrices in 1858.

He developed matrix algebra and its applications in linear transformations.

Explanation

a² - b² = (a - b)(a + b)

a⁴ - b⁴ = (a² - b²)(a² + b²)

= (a - b)(a + b)(a² + b²)

The LCM is (a - b)(a + b)(a² + b²) = (a² - b²)(a² + b²)

= a⁴ - b⁴

Explanation

Given 12 = PQ, we can write P = 12/Q.

For proportion:

4 : Q = P : 3

4/ Q = P / 3

4 × 3 = P × Q

12 = PQ

This matches the given equation.

The answer is 4 : q = p : 3.

Explanation

Loga (m × n) = Loga m + Loga n.

This is a logarithmic property: the log of a product is the sum of the logs.

Explanation

(√x + √y) (√x - √y)

= (√x)² - (√y)²

= x - y

Explanation

x² - xy + y²

= (-2)² - (-2)(2) + (2)²

= 4 + 4 + 4

= 12

Explanation

(3a - 2b)² = (3a)² - 2(3a)(2b) + (2b)²

= 9a² - 12ab + 4b²

Explanation

The expression x² + 7x + 3 has three terms.

A polynomial with three terms is called a trinomial.