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Quadratic Equations
Creative section-A
Problems based on Numbers
a) The product of two consecutive natural numbers is 30.
(i) If one of the numbers is x, write another number in terms of x.
(ii) Find the numbers.
(iii) What number should be added to the smaller one so that the sum of the
squares of two numbers is 85?



Answer :

Let's solve the problem step by step.

### Step (i): Expressing the Second Number
First, let's denote the two consecutive natural numbers as [tex]\( x \)[/tex] and [tex]\( x + 1 \)[/tex].

### Step (ii): Finding the Numbers
We know that the product of these two numbers is 30:
[tex]\[ x \times (x + 1) = 30 \][/tex]

This equation can be expanded and rewritten as:
[tex]\[ x^2 + x - 30 = 0 \][/tex]

This is a quadratic equation in standard form ([tex]\( ax^2 + bx + c = 0 \)[/tex]). We can solve it using the quadratic formula:
[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

For our equation [tex]\( x^2 + x - 30 = 0 \)[/tex], the coefficients are [tex]\( a = 1 \)[/tex], [tex]\( b = 1 \)[/tex], and [tex]\( c = -30 \)[/tex].

Plug these values into the quadratic formula:
[tex]\[ x = \frac{-1 \pm \sqrt{1^2 - 4 \cdot 1 \cdot (-30)}}{2 \cdot 1} \][/tex]

Simplifying inside the square root:
[tex]\[ x = \frac{-1 \pm \sqrt{1 + 120}}{2} \][/tex]
[tex]\[ x = \frac{-1 \pm \sqrt{121}}{2} \][/tex]
[tex]\[ x = \frac{-1 \pm 11}{2} \][/tex]

This gives us two solutions:
[tex]\[ x = \frac{-1 + 11}{2} = \frac{10}{2} = 5 \][/tex]
[tex]\[ x = \frac{-1 - 11}{2} = \frac{-12}{2} = -6 \][/tex]

Since [tex]\( x \)[/tex] represents a natural number, we discard the negative solution. So, [tex]\( x = 5 \)[/tex].

Therefore, the two consecutive natural numbers are:
[tex]\[ x = 5 \][/tex]
[tex]\[ x + 1 = 6 \][/tex]

### Step (iii): Finding the Number to Add to the Smaller Number
We need to determine the number [tex]\( z \)[/tex] that should be added to the smaller number (which is 5) such that the sum of the squares of the two numbers becomes 85.

Let:
[tex]\[ 5 + z \][/tex]
[tex]\[ 6 \][/tex]

The sum of the squares of these two numbers should be equal to 85:
[tex]\[ (5 + z)^2 + 6^2 = 85 \][/tex]

Let's solve this equation step by step:
[tex]\[ (5 + z)^2 + 36 = 85 \][/tex]
[tex]\[ (5 + z)^2 = 85 - 36 \][/tex]
[tex]\[ (5 + z)^2 = 49 \][/tex]

Taking the square root of both sides:
[tex]\[ 5 + z = \pm \sqrt{49} \][/tex]
[tex]\[ 5 + z = \pm 7 \][/tex]

This gives us two solutions:
[tex]\[ 5 + z = 7 \][/tex]
[tex]\[ z = 2 \][/tex]

[tex]\[ 5 + z = -7 \][/tex]
[tex]\[ z = -12 \][/tex]

Since [tex]\( z \)[/tex] represents an additive number and typically, we would consider only non-negative values for such contexts, we take:
[tex]\[ z = 2 \][/tex]

### Conclusion:
1. The two consecutive natural numbers are 5 and 6.
2. The number [tex]\( z \)[/tex] that should be added to the smaller number (5) to make the sum of the squares of the two numbers 85 is [tex]\( z = 2 \)[/tex].

So, the final answer is:
- The two consecutive natural numbers are 5 and 6.
- The number to be added to 5 is 2.