Examples with solutions for Square of sum: Identify the greater value

Exercise #1

(2b+5)2?4b2+25 (2b+5)^2?4b^2+25

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Expand (2b+5)2(2b + 5)^2 using the square of a binomial formula.
  • Step 2: Compare the expanded form with 4b2+254b^2 + 25.
  • Step 3: Determine the relationship between the two expressions based on bb.

Now, let's work through each step:

Step 1: We begin by expanding (2b+5)2(2b + 5)^2. Using the formula for the square of a sum, we have:

(2b+5)2=(2b)2+22b5+52(2b + 5)^2 = (2b)^2 + 2 \cdot 2b \cdot 5 + 5^2

=4b2+20b+25= 4b^2 + 20b + 25

Step 2: We now compare this expression to 4b2+254b^2 + 25:

4b2+20b+254b^2 + 20b + 25 versus 4b2+254b^2 + 25

Step 3: Since 4b2+254b^2 + 25 is shared by both expressions, the comparison depends entirely on the 20b20b term:

If b=0b = 0, both expressions are equal.

If b>0b > 0, (2b+5)2(2b + 5)^2 is greater than 4b2+254b^2 + 25 because 20b>020b > 0.

If b<0b < 0, (2b+5)2(2b + 5)^2 is less than 4b2+254b^2 + 25 because 20b<020b < 0.

Therefore, the relationship between the two expressions depends on the value of bb.

The correct choice is: Depends on the value of b.

Answer

Depends on the value of b

Exercise #2

Replace '?' with the missing sign
x(2x+3)?2(x+3)2 x(2x+3)?2(x+3)^2

given that 0 < x

Video Solution

Step-by-Step Solution

Let's work through determining the relationship between the expressions by expanding and comparing them.

First, expand the right-hand expression 2(x+3)2 2(x+3)^2 :

  • Start with the binomial expansion: (x+3)2=x2+6x+9 (x+3)^2 = x^2 + 6x + 9 .
  • Multiply through by 2: 2(x2+6x+9)=2x2+12x+18 2(x^2 + 6x + 9) = 2x^2 + 12x + 18 .

Now, consider the left-hand expression x(2x+3) x(2x+3) :

  • Distribute x x : x2x+x3=2x2+3x x \cdot 2x + x \cdot 3 = 2x^2 + 3x .

We now have the expanded expressions:

  • Left: 2x2+3x 2x^2 + 3x
  • Right: 2x2+12x+18 2x^2 + 12x + 18

To compare these, subtract the left expression from the right:

(2x2+12x+18)(2x2+3x)=9x+18 (2x^2 + 12x + 18) - (2x^2 + 3x) = 9x + 18

The result 9x+18 9x + 18 shows that for any positive x x , 9x+18 9x + 18 is greater than 0 since both terms are positive. Hence, the right side is always larger than the left side.

Therefore, x(2x+3)<2(x+3)2 x(2x+3) < 2(x+3)^2 for x>0 x > 0 .

The correct inequality is < < .

Answer

<

Exercise #3

Replace '?' with the missing symbol

1+(5+x)2+3x 2?5x2+10x+25 1+(5+x)^2+3x_{\text{ }}^2?5x^2+10x+25

given that 0 < x < 1

Video Solution

Step-by-Step Solution

To solve this problem, we'll start by expanding both expressions to compare them.

First, expand the left expression:

1+(5+x)2+3x2 1 + (5 + x)^2 + 3x^2

Using the formula for expanding a square, (5+x)2(5 + x)^2 becomes:

52+25x+x2=25+10x+x2 5^2 + 2 \cdot 5 \cdot x + x^2 = 25 + 10x + x^2

Thus, the left-hand expression becomes:

1+25+10x+x2+3x2=26+10x+4x2 1 + 25 + 10x + x^2 + 3x^2 = 26 + 10x + 4x^2

Next, simplify the right-hand side:

5x2+10x+25 5x^2 + 10x + 25

Now, compare both simplified expressions:

  • Left: 26+10x+4x2 26 + 10x + 4x^2
  • Right: 5x2+10x+25 5x^2 + 10x + 25

Subtract the right expression from the left to see which is greater:

(26+10x+4x2)(5x2+10x+25) (26 + 10x + 4x^2) - (5x^2 + 10x + 25)

=26+10x+4x25x210x25 = 26 + 10x + 4x^2 - 5x^2 - 10x - 25

=1x2 = 1 - x^2

Since 0<x<10 < x < 1, it follows that 1<x2<0-1 < -x^2 < 0, making 1x21 - x^2 positive.

Therefore, the expression on the left is greater than the expression on the right:

1+(5+x)2+3x2>5x2+10x+25 1 + (5 + x)^2 + 3x^2 \gt 5x^2 + 10x + 25 .

Answer

>

Exercise #4

Replace ? with the missing sign given that m3+2m2n=4m2+n2 m^3+2m^2n=4m^2+n^2 :

m(m+n)2?(2m+n)2 m(m+n)^2?(2m+n)^2

Video Solution

Step-by-Step Solution

To solve this problem, we aim to relate the expression m(m+n)2 m(m+n)^2 and (2m+n)2 (2m+n)^2 given the equation m3+2m2n=4m2+n2 m^3 + 2m^2n = 4m^2 + n^2 .

The key step is to understand that due to the given constraint equation, without loss of generality or additional specific values for m m and n n , a direct comparison to determine the sign ? ? is not feasible under the constraint m3+2m2n=4m2+n2 m^3 + 2m^2n = 4m^2 + n^2 . The nature of the relationship defined by the constraint tells us that the relationship between these expressions might hold under special conditions, but projecting one side as definitively greater, less, or equal is not straightforward.

Given this complexity and the lack of further simplifiable information directly provided by the equation, it is not possible to calculate or visually confirm which sign should be appropriately used without more specific values or further simplification details.

Therefore, the answer is: It is not possible to calculate.

Answer

It is not possible to calculate.

Exercise #5

0 < a,b

Fill in the corresponding sign

a(ab)2?a(a+b)2ab2 a(a-b)^2?a(a+b)^2-ab^2

Video Solution

Step-by-Step Solution

The task is to determine the inequality a(ab)2a(a-b)^2 compared to a(a+b)2ab2a(a+b)^2 - ab^2 given 0<a,b0 < a, b. Here's how to solve it:

First, let's expand and simplify each expression:

Starting with a(ab)2a(a-b)^2, expand as follows:

  • (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2.
  • Multiplying by aa gives: a(a22ab+b2)=a32a2b+ab2a(a^2 - 2ab + b^2) = a^3 - 2a^2b + ab^2.

Next, expand a(a+b)2ab2a(a+b)^2-ab^2:

  • (a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2ab + b^2.
  • Multiplying by aa gives: a(a2+2ab+b2)=a3+2a2b+ab2a(a^2 + 2ab + b^2) = a^3 + 2a^2b + ab^2.
  • Subtracting ab2ab^2 yields: a3+2a2b+ab2ab2=a3+2a2ba^3 + 2a^2b + ab^2 - ab^2 = a^3 + 2a^2b.

Now compare the two expressions:

  • a(ab)2=a32a2b+ab2a(a-b)^2 = a^3 - 2a^2b + ab^2.
  • a(a+b)2ab2=a3+2a2ba(a+b)^2 - ab^2 = a^3 + 2a^2b.
  • The inequality a(ab)2?a(a+b)2ab2a(a-b)^2 ? a(a+b)^2 - ab^2 is simplified to:\)
  • a32a2b+ab2<a3+2a2ba^3 - 2a^2b + ab^2 < a^3 + 2a^2b.
  • Cancel a3a^3 from both sides: 2a2b+ab2<2a2b-2a^2b + ab^2 < 2a^2b.
  • Bring like terms together: 4a2b+ab2<0-4a^2b + ab^2 < 0.
  • Factor bb: b(4a2+ab)<0b(-4a^2 + ab) < 0.

Given b>0b > 0, divide through by bb:

4a2+ab<0-4a^2 + ab < 0, or equivalently 4a2<ab-4a^2 < -ab, hence 4a>b4a > b.

Therefore, a>b4a > \frac{b}{4}.

The inequality holds as a(ab)2<a(a+b)2ab2a(a-b)^2 < a(a+b)^2 - ab^2 when a>b4a > \frac{b}{4}.

Therefore, the correct choice is:

< < When a>b4 a > \frac{b}{4}

Answer

< When a>\frac{b}{4}

Exercise #6

8a2+28a+1?(8a+1)2 8a^2+2\sqrt{8}a+1?(\sqrt{8}a+1)^2

Video Solution

Answer

= =