Find the zeros of f(x) = 4x2 + 5x - 21. {-7/4, 3} {7/4, -3} {3/4, -7}

x = - 3, x =

Step-by-step explanation:

Given

f(x) = 4x² + 5x - 21

To obtain the zeros, equate f(x) to zero, that is

4x² + 5x - 21 = 0

Consider the factors of the product of the coefficient of the x² term and the constant term which sum to give the coefficient of the x- term

product = 4 × - 21 = - 84 and sum = + 5

The factors are + 12 and - 7

Use these factors to split the x- term

4x² + 12x - 7x - 21 = 0 ( factor the first/second and third/fourth terms )

4x(x + 3) - 7(x + 3) = 0 ← factor out (x + 3) from each term

(x + 3)(4x - 7) = 0

Equate each factor to zero and solve for x

x + 3 = 0 ⇒ x = - 3

4x - 7 = 0 ⇒ 4x = 7 ⇒ x =

x= -3

step-by-step explanation:

step 1: simplify brackets

4 - x - 1 = 6

step 2: simpilfy

3 - x = 6

step 3: subtract 3 from both sides

-x = 6 - 3

step 4: simpilfy 6 - 3

-x = 3

step 5: multiply both sides by -1

x = -3

step-by-step explanation: