Malik asked his teacher if there was a way to check his answer after writing equivalent expressions. What should be his teacher’s response?
Choose a number to substitute for the variable. Find the value of each expression. If the values are even, the expressions are equivalent.
Substitute a number for the variable. If the simplified expressions have the same value, the expressions are equivalent.
Multiply each expression by the same number. If the expressions are equal, the expressions are equivalent.
Add a number to each expression. If the simplified expressions are equal, the expressions are equivalent.

step-by-step explanation:

a

step-by-step explanation:

the answer is a

yx = 36

step-by-step explanation:

cos f = opposite side/ hypotenuse

cos f = yw / yx

we know cos f = 4/9 and yw =16

4/9 = 16/yx

multiply each side by yx

4/9 yx = 16/ yx * yx

4/9 yx = 16

multiply each side by 9/4

9/4 * 4/9 yx = 16 *9/4

yx = 36

x^2 + 81

we can factor this using difference of square binomials.

rewrite the equation:

x^2 - (-81)

factor:

(a^2 - b^2) = (√a^2 + √b^2)(√a^2 - √b^2)

(x^2 - (-81) = (x + √-81)(x - √-81)

we can remove the - from under the radical by multiplying it by i.

(x^2 - (-81) = (x + i√81)(x - i√81)

(x^2 - (-81) = (x + 9i)(x - 9i)

we can check our answer by using foil:

x^2 - 9ix + 9ix - 81i^2

x^2 - 81^2

i^2 = -1

x^2 + 81