A matrix is diagonal if
In other words, you want non-zero elements only when the indices of the row and the column are the same: the first element of the first row must be non zero, the second element of the second row must be non-zero, and so on. All other elements must be zero.
Remmeber, you can do anything to an equation as long as you do it to both sides
for inequalities, if you multiply or divide both sides by a negive, flip the direction of the inequality sign
pemdas always applies
but also the commutative property and assiociative property
so
2(5y+13)-6<20
add 6 both sides
2(5y+13)<26
divide both sides by 2 (easier that distributing)
5y+13<13
minus 13 both sides
5y<0
y<0 is the solution
<h3>
Answer: 80 meters</h3>
This is an isosceles triangle. The dashed line is the height which is perpendicular to the base 120. The height is always perpendicular to the base. The dashed line cuts the base into two equal pieces (this only works for isosceles triangles when you cut at the vertex like this).
So we have two smaller triangles each with a base of 60 and a height of x. Focus on one of the right triangles and use the pythagorean theorem to solve for x.
a^2 + b^2 = c^2
x^2 + (60)^2 = (100)^2
x^2 + 3600 = 10000
x^2 = 10000 - 3600
x^2 = 6400
x = sqrt(6400)
x = 80
Each smaller right triangle has side lengths of 60, 80, 100
Note the ratio 60:80:100 reduces to 3:4:5. A 3-4-5 right triangle is a very common pythagorean primitive.
98cm^2 - bigger triangles are 28 each, bottom one is 14. (28 x 3) + 14=98
If we want rice per person, that's
1a. Answer: 25/3
That's between 24/3 and 27/3 i.e. between
1b. Answer: 8 and 9
