Question

If x=4
find 7 x^2 (3 x- 9)​

Answer 1

Given

• x = 4

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To Find

• Value of the expression with the given value of variable ⇒ 7x² (3x - 9)

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Solution

We know that x = 4

So now we have two methods to find the value of this expression.

Method 1

Simplify the expression.

⇒ 7x² (3x - 9)

⇒ 7x² (3x) - 7x² (9)

⇒ 21x³ - 63x²

Now substitute the value of 'x' with 4.

⇒ 21x³ - 63x²

⇒ 21 (4)³ - 63 (4)²

⇒ 21 (64) - 63 (16)

⇒ 1344 - 1008

⇒ 336

Method 2

Substitute the value of 'x' with 4 and solve accordingly.

⇒ 7x² (3x - 9)

⇒ 7 (4)² [3 (4) - 9]

⇒ 7 (16) [12 - 9]

⇒ 112 (12 - 9)

⇒ 112 (3)

⇒ 336

∴ The value of the expression 7x² (3x - 9) is 336 when the value of 'x' is 4.

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Answer 2

Question -

If x = 4 ; find 7x² (3x - 9)

Answer -

Given that -

• Value of x = 4

To find -

• Value of expression with 7x² (3x - 9)

Solution -

• 7x² (3x - 9) = 336

What does the question say ?

Let's understand that concept 1st !

• This question says that there is a equation given that is 7x² (3x - 9) then the question says that the value of x = 4 then we have to solve this.

How to do this question ?

Let's see the procedure now !

• To solve this question, we have to follow the procedure. Frankly saying then there are many ways to solve this question but let's see the easiest way according to me to solve this problem. Now, continuing... To solve this question we have to put the 4 in the place of x . Afterwards putting the values we get our final result very easily. Let's see it properly.

Full solution -

☞ 7x² (3x - 9)

Putting 4 in the place of x we get the following results.

☞ 7(4)² (3×4 -9)

☞ 7(16) (12-9)

☞ 7 × 16 (12-9)

☞ 112 (12-9)

☞ 112(3)

☞ 112 × 3

☞ 336

Hence, 336 is the correct answer ; means 7x² (3x - 9) values 336 when putting 4 as x.