Question

The value of the polynomial 7x4

+ 3x2

- 4, when x = - 2 is:



a) 100 b) 110 c) 120 d) 130​

Answer 1

Step-by-step explanation:

At x = -2

7(-2)⁴ + 3(-2)² - 4

7(16) + 3(4) - 4

112 + 12 - 4 = 124-4 = 120

Answer 2

Given:

• A Polynomial 7$x^4$+3$x^2$-4
• x = -2

To Find:

• The value of the given polynomial.

Solution:

Let,

7$x^4$+3$x^2$ - 4→ {equation 1}

We have the value of "x", by substituting it in equation 1 we get the value of the polynomial.

⇒ 7$x^4$+3$x^2$-4 = 7×$(-2)^4$ + 3× $(-2)^2$-4 {squaring the terms}

⇒ 7$x^4$+3$x^2$-4 = (7×16) + (3×4) - 4 {multiplying the terms}

⇒ 7$x^4$+3$x^2$-4= 112+12-4 {adding and further subtracting the terms}

⇒ 7$x^4$+3$x^2$-4 = 120

∴  The value of 7$x^4$+3$x^2$-4 = 120. (option c)