Please answer either or all of them and please show me how you solve it

Step-by-step explanation:

using pythagoras theorem

a^2 + b^2 = c^2

4^2 + y^2 = 21^2

16 + y^2 = 441

y^2 = 441 - 16

y^2 = 425

y = 13.2

a^2 + b^2 = c^2

4^2 + x^2 = 7^2

16 + x^2 = 49

x^2 = 40 - 16

x^2 = 33

x =

x = 5.7 m

the sum of the lengths of any two sides of a triangle is greater than the length of the third side. if you take the three sides of a triangle and add them in pairs, the sum is greater than (not equal to) the third side. if that is not true, then it is not possible to construct a triangle with the given side lengths.

step-by-step explanation: