Question

Answer any one pls help pls

Answer 1

this is the answer of your
second question
This is the answer of 1st BC=4CD,CD=BC/4
BD=3CD=3BC/4 (1)
IN ∆ABD,AB^2=AD^2+BD^2 (2)
IN ∆ACD AC^2 =AD^2+CD^2 (3)
NOW AB^2-AC^2=BD^2=CD^2
=9BC^2/16-BC^2/16=BC^2/2
2(AB^2-AC^2)=BC^2
2AB^2=2AC^2+BC^2

Answer 2

hello...........

DB=3CD
DB=3/4BC
CD=1/4BC
In right ΔADB,
AB²=AD²+DB²                ..........[1]

In rightΔADC,
AC²=AD²+CD²               ...........[2]

Subtracting [2] from [1] , we have 
AB²-AC²=DB²+AD²-CD²-AD²
AB²-AC²=DB²-CD²
             =[3/4 BC]² -[1/4 BC]²
             =9/16 BC² - 1/16 BC²
             =8/16 BC²
AB²-AC²=1/2BC²
2AB²-2AC²=BC²
        2AB² =BC² + 2 AC²
Hence prove

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Hope this would help you
@Rohit