Help me to solve this fast ( prove it)

Step-by-step explanation:

sec⁴A + tan⁴A = 1 + (2tan²A/cos²A)

LHS = sec⁴A + tan⁴A

= (sec²A)² + (tan²A)² {using formula of a²+b²)

= (sec²A-tan²A) + 2tan²A.sec²A

= 1 + {2tan²A.(1/cos²A)}

= 1 + (2tan²A/cos²A)

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -