Rearrange x - 3y = 9 to make x the subject by adding 3y to both sides of the equation, giving x = 9 + 3y. Substitute the value of "x" in the second equation for "9 + 3y", giving: 5(9 + 3y) + y = 21. Multiply out the brackets to give 45 + 15y + y = 21. Add together like terms: 45 + 16y = 21, then subtract 45 from both sides: 16y = -24, and then ...

rearrange the first equation so it reads y= 5x+y= 21 y=21-5xSubstitute this y value into the second equation x-3y=9 y=21-5x x-3(21-5x)=9Expand out the bracket and rearrange to find out what x equals ( be careful with the changing plus and minus) x-63+ 15x=9 16x-63=9 16x=72 x=4.5REMEMBER you need to find x and Y so put your x value back into on ...

The equations become:5x + y = 215x - 15y = 45Then subtract one from the other to eradicate x.y - - 15 y = 16y and 21 - 45 = -2416y = -24Solve for y.y = -24/16 (both divisible by 8) so y = -3/2 or -1.5Insert y into either of the original equations.x - (-3*3/2) = 9x + 9/2 = 9 x = 9 - 9/2 x = 18/2 - 9/2 x = 9/2 or 4.5So: x = 4.5 y = -1.5

Then, to get x, divide through by 4 for x=3. That’s one half of the answer, now to get y, sub x=4 into one of the equations and rearrange for y. Subbing it into the top one: 5(4) + y = 21 so 20+y=21 and y=1. So, x=4 and y=1.

factorise x^2+10x+21 firstly the largest power is x^2 so when factorising we know that both brackets must involve an x plus or minus a number. next we look at the 21 and we need two numbers that multiply together to get this number, the two sets of numbers that multiply to get this is 1 and 21 and 3 and 7.

Harry mixes white paint and blue paint in the ratio 2:5. He makes a total of 21 litres of paint. How much more blue paint does he need to add to the mixture so that the ratio of white paint to blue paint becomes 1:4?

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y = mx + c m is the gradient and c is the y-interceptUse values for A, x=5 y=9 and m=3so 9 = (3 x 5) + c 9 = 15 + c c = -6Then use coordinates for B, x=d y=15 and... Find a tutor How it works Prices Resources

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Solve these simultaneous equations: 2x + 3y = 19 and x + 4y = 17. Answered by James H. From factorising a^2-b^2 hence or otherwise simplify fully (x^2 + 4)^2 - (x^2-2)^2